From: Matthias Brugger <matthias.bgg@xxxxxxxxx> Some devices like SoCs from Mediatek need to use the clock through a regmap interface. This patch adds regmap support for the simple multiplexer clock, the divider clock and the clock gate code. Signed-off-by: Matthias Brugger <matthias.bgg@xxxxxxxxx> Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx> --- drivers/clk/Makefile | 1 + drivers/clk/clk-divider.c | 68 +++++++++++++++++++++++++------- drivers/clk/clk-gate.c | 54 +++++++++++++++++++------ drivers/clk/clk-io.c | 48 ++++++++++++++++++++++ drivers/clk/clk-io.h | 22 +++++++++++ drivers/clk/clk-mux.c | 94 +++++++++++++++++++++++++++++++++++++------- include/linux/clk-provider.h | 54 +++++++++++++++++++++++-- 7 files changed, 298 insertions(+), 43 deletions(-) create mode 100644 drivers/clk/clk-io.c create mode 100644 drivers/clk/clk-io.h diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile index 820714c72d36..31a888c0c182 100644 --- a/drivers/clk/Makefile +++ b/drivers/clk/Makefile @@ -11,6 +11,7 @@ obj-$(CONFIG_COMMON_CLK) += clk-mux.o obj-$(CONFIG_COMMON_CLK) += clk-composite.o obj-$(CONFIG_COMMON_CLK) += clk-fractional-divider.o obj-$(CONFIG_COMMON_CLK) += clk-gpio.o +obj-$(CONFIG_COMMON_CLK) += clk-io.o ifeq ($(CONFIG_OF), y) obj-$(CONFIG_COMMON_CLK) += clk-conf.o endif diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c index 3ace102a2a0a..1ddb353b3fff 100644 --- a/drivers/clk/clk-divider.c +++ b/drivers/clk/clk-divider.c @@ -18,6 +18,8 @@ #include <linux/string.h> #include <linux/log2.h> +#include "clk-io.h" + /* * DOC: basic adjustable divider clock that cannot gate * @@ -142,7 +144,8 @@ static unsigned long clk_divider_recalc_rate(struct clk_hw *hw, struct clk_divider *divider = to_clk_divider(hw); unsigned int val; - val = clk_readl(divider->reg) >> divider->shift; + val = clk_io_readl(hw, divider->reg, divider->regmap, divider->offset); + val >>= divider->shift; val &= div_mask(divider->width); return divider_recalc_rate(hw, parent_rate, val, divider->table, @@ -354,7 +357,10 @@ static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate, /* if read only, just return current value */ if (divider->flags & CLK_DIVIDER_READ_ONLY) { - bestdiv = readl(divider->reg) >> divider->shift; + bestdiv = clk_io_readl(hw, divider->reg, divider->regmap, + divider->offset); + + bestdiv >>= divider->shift; bestdiv &= div_mask(divider->width); bestdiv = _get_div(divider->table, bestdiv, divider->flags, divider->width); @@ -400,12 +406,16 @@ static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate, if (divider->flags & CLK_DIVIDER_HIWORD_MASK) { val = div_mask(divider->width) << (divider->shift + 16); + val |= value << divider->shift; + clk_io_writel(hw, divider->reg, divider->regmap, + divider->offset, val); } else { - val = clk_readl(divider->reg); - val &= ~(div_mask(divider->width) << divider->shift); + u32 mask = div_mask(divider->width) << divider->shift; + + val = value << divider->shift; + clk_io_update_bits(hw, divider->reg, divider->regmap, + divider->offset, mask, val); } - val |= value << divider->shift; - clk_writel(val, divider->reg); if (divider->lock) spin_unlock_irqrestore(divider->lock, flags); @@ -424,9 +434,9 @@ EXPORT_SYMBOL_GPL(clk_divider_ops); static struct clk *_register_divider(struct device *dev, const char *name, const char *parent_name, unsigned long flags, - void __iomem *reg, u8 shift, u8 width, - u8 clk_divider_flags, const struct clk_div_table *table, - spinlock_t *lock) + void __iomem *reg, struct regmap *regmap, u32 offset, + u8 shift, u8 width, u8 clk_divider_flags, + const struct clk_div_table *table, spinlock_t *lock) { struct clk_divider *div; struct clk *clk; @@ -451,7 +461,12 @@ static struct clk *_register_divider(struct device *dev, const char *name, init.num_parents = (parent_name ? 1 : 0); /* struct clk_divider assignments */ - div->reg = reg; + if (flags & CLK_USE_REGMAP) + div->regmap = regmap; + else + div->reg = reg; + + div->offset = offset; div->shift = shift; div->width = width; div->flags = clk_divider_flags; @@ -485,8 +500,8 @@ struct clk *clk_register_divider(struct device *dev, const char *name, void __iomem *reg, u8 shift, u8 width, u8 clk_divider_flags, spinlock_t *lock) { - return _register_divider(dev, name, parent_name, flags, reg, shift, - width, clk_divider_flags, NULL, lock); + return _register_divider(dev, name, parent_name, flags, reg, NULL, 0, + shift, width, clk_divider_flags, NULL, lock); } EXPORT_SYMBOL_GPL(clk_register_divider); @@ -510,8 +525,8 @@ struct clk *clk_register_divider_table(struct device *dev, const char *name, u8 clk_divider_flags, const struct clk_div_table *table, spinlock_t *lock) { - return _register_divider(dev, name, parent_name, flags, reg, shift, - width, clk_divider_flags, table, lock); + return _register_divider(dev, name, parent_name, flags, reg, NULL, 0, + shift, width, clk_divider_flags, table, lock); } EXPORT_SYMBOL_GPL(clk_register_divider_table); @@ -530,3 +545,28 @@ void clk_unregister_divider(struct clk *clk) kfree(div); } EXPORT_SYMBOL_GPL(clk_unregister_divider); + +struct clk *clk_regm_register_divider(struct device *dev, const char *name, + const char *parent_name, unsigned long flags, + struct regmap *regmap, u32 offset, u8 shift, u8 width, + u8 clk_divider_flags, spinlock_t *lock) +{ + flags |= CLK_USE_REGMAP; + + return _register_divider(dev, name, parent_name, flags, NULL, regmap, + offset, shift, width, clk_divider_flags, NULL, lock); +} +EXPORT_SYMBOL_GPL(clk_regm_register_divider); + +struct clk *clk_regm_register_divider_table(struct device *dev, + const char *name, const char *parent_name, unsigned long flags, + struct regmap *regmap, u32 offset, u8 shift, u8 width, + u8 clk_divider_flags, const struct clk_div_table *table, + spinlock_t *lock) +{ + flags |= CLK_USE_REGMAP; + + return _register_divider(dev, name, parent_name, flags, NULL, regmap, + offset, shift, width, clk_divider_flags, table, lock); +} +EXPORT_SYMBOL_GPL(clk_regm_register_divider_table); diff --git a/drivers/clk/clk-gate.c b/drivers/clk/clk-gate.c index de0b322f5f58..38b558397631 100644 --- a/drivers/clk/clk-gate.c +++ b/drivers/clk/clk-gate.c @@ -16,6 +16,8 @@ #include <linux/err.h> #include <linux/string.h> +#include "clk-io.h" + /** * DOC: basic gatable clock which can gate and ungate it's ouput * @@ -46,7 +48,7 @@ static void clk_gate_endisable(struct clk_hw *hw, int enable) struct clk_gate *gate = to_clk_gate(hw); int set = gate->flags & CLK_GATE_SET_TO_DISABLE ? 1 : 0; unsigned long uninitialized_var(flags); - u32 reg; + u32 reg, mask; set ^= enable; @@ -59,16 +61,20 @@ static void clk_gate_endisable(struct clk_hw *hw, int enable) reg = BIT(gate->bit_idx + 16); if (set) reg |= BIT(gate->bit_idx); - } else { - reg = clk_readl(gate->reg); + clk_io_writel(hw, gate->reg, gate->regmap, gate->offset, reg); + } else { if (set) - reg |= BIT(gate->bit_idx); + reg = BIT(gate->bit_idx); else - reg &= ~BIT(gate->bit_idx); + reg = 0x0; + + mask = BIT(gate->bit_idx); + + clk_io_update_bits(hw, gate->reg, gate->regmap, gate->offset, + mask, reg); } - clk_writel(reg, gate->reg); if (gate->lock) spin_unlock_irqrestore(gate->lock, flags); @@ -93,7 +99,7 @@ static int clk_gate_is_enabled(struct clk_hw *hw) u32 reg; struct clk_gate *gate = to_clk_gate(hw); - reg = clk_readl(gate->reg); + reg = clk_io_readl(hw, gate->reg, gate->regmap, gate->offset); /* if a set bit disables this clk, flip it before masking */ if (gate->flags & CLK_GATE_SET_TO_DISABLE) @@ -122,10 +128,10 @@ EXPORT_SYMBOL_GPL(clk_gate_ops); * @clk_gate_flags: gate-specific flags for this clock * @lock: shared register lock for this clock */ -struct clk *clk_register_gate(struct device *dev, const char *name, +struct clk *__clk_register_gate(struct device *dev, const char *name, const char *parent_name, unsigned long flags, - void __iomem *reg, u8 bit_idx, - u8 clk_gate_flags, spinlock_t *lock) + void __iomem *reg, struct regmap *regmap, u32 offset, + u8 bit_idx, u8 clk_gate_flags, spinlock_t *lock) { struct clk_gate *gate; struct clk *clk; @@ -150,7 +156,12 @@ struct clk *clk_register_gate(struct device *dev, const char *name, init.num_parents = (parent_name ? 1 : 0); /* struct clk_gate assignments */ - gate->reg = reg; + if (flags & CLK_USE_REGMAP) + gate->regmap = regmap; + else + gate->reg = reg; + + gate->offset = offset; gate->bit_idx = bit_idx; gate->flags = clk_gate_flags; gate->lock = lock; @@ -163,6 +174,15 @@ struct clk *clk_register_gate(struct device *dev, const char *name, return clk; } + +struct clk *clk_register_gate(struct device *dev, const char *name, + const char *parent_name, unsigned long flags, + void __iomem *reg, u8 bit_idx, + u8 clk_gate_flags, spinlock_t *lock) +{ + return __clk_register_gate(dev, name, parent_name, flags, + reg, NULL, 0, bit_idx, clk_gate_flags, lock); +} EXPORT_SYMBOL_GPL(clk_register_gate); void clk_unregister_gate(struct clk *clk) @@ -180,3 +200,15 @@ void clk_unregister_gate(struct clk *clk) kfree(gate); } EXPORT_SYMBOL_GPL(clk_unregister_gate); + +struct clk *clk_regm_register_gate(struct device *dev, const char *name, + const char *parent_name, unsigned long flags, + struct regmap *regmap, u32 offset, u8 bit_idx, + u8 clk_gate_flags, spinlock_t *lock) +{ + flags |= CLK_USE_REGMAP; + + return __clk_register_gate(dev, name, parent_name, flags, + NULL, regmap, offset, bit_idx, clk_gate_flags, lock); +} +EXPORT_SYMBOL_GPL(clk_regm_register_gate); diff --git a/drivers/clk/clk-io.c b/drivers/clk/clk-io.c new file mode 100644 index 000000000000..ceeb64e15ddb --- /dev/null +++ b/drivers/clk/clk-io.c @@ -0,0 +1,48 @@ +/* + * Copyright (C) 2015 Matthias Brugger <matthias.bgg@xxxxxxxxx> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + */ + +#include <linux/clk-provider.h> + +void clk_io_writel(struct clk_hw *hw, void __iomem *reg, struct regmap *regmap, + u32 offset, u32 val) +{ + if (__clk_get_flags(hw->clk) & CLK_USE_REGMAP) + regmap_write(regmap, offset, val); + else + clk_writel(val, reg); +} + +u32 clk_io_readl(struct clk_hw *hw, void __iomem *reg, struct regmap *regmap, + u32 offset) +{ + u32 val; + + if (__clk_get_flags(hw->clk) & CLK_USE_REGMAP) + regmap_read(regmap, offset, &val); + else + val = clk_readl(reg); + + return val; +} + +int clk_io_update_bits(struct clk_hw *hw, void __iomem *reg, + struct regmap *regmap, u32 offset, u32 mask, u32 val) +{ + unsigned int tmp; + + if (__clk_get_flags(hw->clk) & CLK_USE_REGMAP) + return regmap_update_bits(regmap, offset, mask, val); + + tmp = clk_readl(reg); + tmp &= ~mask; + tmp |= val; + clk_writel(tmp, reg); + + return 0; +} diff --git a/drivers/clk/clk-io.h b/drivers/clk/clk-io.h new file mode 100644 index 000000000000..b5599ba02084 --- /dev/null +++ b/drivers/clk/clk-io.h @@ -0,0 +1,22 @@ +/* + * linux/drivers/clk/clk-io.h + * + * Copyright (C) 2015 Matthias Brugger <matthias.bgg@xxxxxxxxx> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ +#ifndef __LINUX_CLK_IO_H +#define __LINUX_CLK_IO_H + +#include <linux/clk-provider.h> + +void clk_io_writel(struct clk_hw *hw, void __iomem *reg, struct regmap *regmap, + u32 offset, u32 val); +u32 clk_io_readl(struct clk_hw *hw, void __iomem *reg, struct regmap *regmap, + u32 offset); +int clk_io_update_bits(struct clk_hw *hw, void __iomem *reg, + struct regmap *regmap, u32 offset, u32 mask, u32 val); + +#endif diff --git a/drivers/clk/clk-mux.c b/drivers/clk/clk-mux.c index 7129c86a79db..d3831eca8b56 100644 --- a/drivers/clk/clk-mux.c +++ b/drivers/clk/clk-mux.c @@ -16,6 +16,8 @@ #include <linux/io.h> #include <linux/err.h> +#include "clk-io.h" + /* * DOC: basic adjustable multiplexer clock that cannot gate * @@ -41,7 +43,9 @@ static u8 clk_mux_get_parent(struct clk_hw *hw) * OTOH, pmd_trace_clk_mux_ck uses a separate bit for each clock, so * val = 0x4 really means "bit 2, index starts at bit 0" */ - val = clk_readl(mux->reg) >> mux->shift; + val = clk_io_readl(hw, mux->reg, mux->regmap, mux->offset); + + val >>= mux->shift; val &= mux->mask; if (mux->table) { @@ -70,6 +74,7 @@ static int clk_mux_set_parent(struct clk_hw *hw, u8 index) struct clk_mux *mux = to_clk_mux(hw); u32 val; unsigned long flags = 0; + int ret = 0; if (mux->table) index = mux->table[index]; @@ -89,19 +94,22 @@ static int clk_mux_set_parent(struct clk_hw *hw, u8 index) if (mux->flags & CLK_MUX_HIWORD_MASK) { val = mux->mask << (mux->shift + 16); + val |= index << mux->shift; + clk_io_writel(hw, mux->reg, mux->regmap, mux->offset, val); } else { - val = clk_readl(mux->reg); - val &= ~(mux->mask << mux->shift); + u32 mask = mux->mask << mux->shift; + + val = index << mux->shift; + ret = clk_io_update_bits(hw, mux->reg, mux->regmap, + mux->offset, mask, val); } - val |= index << mux->shift; - clk_writel(val, mux->reg); if (mux->lock) spin_unlock_irqrestore(mux->lock, flags); else __release(mux->lock); - return 0; + return ret; } const struct clk_ops clk_mux_ops = { @@ -116,10 +124,11 @@ const struct clk_ops clk_mux_ro_ops = { }; EXPORT_SYMBOL_GPL(clk_mux_ro_ops); -struct clk *clk_register_mux_table(struct device *dev, const char *name, +struct clk *__clk_register_mux_table(struct device *dev, const char *name, const char * const *parent_names, u8 num_parents, unsigned long flags, - void __iomem *reg, u8 shift, u32 mask, + void __iomem *reg, struct regmap *regmap, + u32 offset, u8 shift, u32 mask, u8 clk_mux_flags, u32 *table, spinlock_t *lock) { struct clk_mux *mux; @@ -152,7 +161,12 @@ struct clk *clk_register_mux_table(struct device *dev, const char *name, init.num_parents = num_parents; /* struct clk_mux assignments */ - mux->reg = reg; + if (flags & CLK_USE_REGMAP) + mux->regmap = regmap; + else + mux->reg = reg; + + mux->offset = offset; mux->shift = shift; mux->mask = mask; mux->flags = clk_mux_flags; @@ -167,19 +181,40 @@ struct clk *clk_register_mux_table(struct device *dev, const char *name, return clk; } + +struct clk *clk_register_mux_table(struct device *dev, const char *name, + const char * const *parent_names, u8 num_parents, + unsigned long flags, void __iomem *reg, u8 shift, u32 mask, + u8 clk_mux_flags, u32 *table, spinlock_t *lock) +{ + return __clk_register_mux_table(dev, name, parent_names, num_parents, + flags, reg, NULL, 0, + shift, mask, clk_mux_flags, + table, lock); +} EXPORT_SYMBOL_GPL(clk_register_mux_table); -struct clk *clk_register_mux(struct device *dev, const char *name, +struct clk *__clk_register_mux(struct device *dev, const char *name, const char * const *parent_names, u8 num_parents, - unsigned long flags, - void __iomem *reg, u8 shift, u8 width, + unsigned long flags, void __iomem *reg, struct regmap *regmap, + u32 offset, u8 shift, u8 width, u8 clk_mux_flags, spinlock_t *lock) { u32 mask = BIT(width) - 1; - return clk_register_mux_table(dev, name, parent_names, num_parents, - flags, reg, shift, mask, clk_mux_flags, - NULL, lock); + return __clk_register_mux_table(dev, name, parent_names, num_parents, + flags, reg, regmap, offset, shift, mask, + clk_mux_flags, NULL, lock); +} + +struct clk *clk_register_mux(struct device *dev, const char *name, + const char * const *parent_names, u8 num_parents, + unsigned long flags, void __iomem *reg, u8 shift, u8 width, + u8 clk_mux_flags, spinlock_t *lock) +{ + return __clk_register_mux(dev, name, parent_names, num_parents, flags, + reg, NULL, 0, shift, width, + clk_mux_flags, lock); } EXPORT_SYMBOL_GPL(clk_register_mux); @@ -198,3 +233,32 @@ void clk_unregister_mux(struct clk *clk) kfree(mux); } EXPORT_SYMBOL_GPL(clk_unregister_mux); + +struct clk *clk_regm_register_mux(struct device *dev, const char *name, + const char * const *parent_names, u8 num_parents, + unsigned long flags, struct regmap *regmap, + u32 offset, u8 shift, u8 width, + u8 clk_mux_flags, spinlock_t *lock) +{ + flags |= CLK_USE_REGMAP; + + return __clk_register_mux(dev, name, parent_names, num_parents, flags, + NULL, regmap, offset, shift, width, + clk_mux_flags, lock); +} +EXPORT_SYMBOL_GPL(clk_regm_register_mux); + +struct clk *clk_regm_register_mux_table(struct device *dev, const char *name, + const char * const *parent_names, u8 num_parents, + unsigned long flags, struct regmap *regmap, + u32 offset, u8 shift, u32 mask, + u8 clk_mux_flags, u32 *table, spinlock_t *lock) +{ + flags |= CLK_USE_REGMAP; + + return __clk_register_mux_table(dev, name, parent_names, num_parents, + flags, NULL, regmap, offset, + shift, mask, clk_mux_flags, + table, lock); +} +EXPORT_SYMBOL_GPL(clk_regm_register_mux_table); diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h index c56988ac63f7..0c55a37cf8f7 100644 --- a/include/linux/clk-provider.h +++ b/include/linux/clk-provider.h @@ -13,6 +13,7 @@ #include <linux/io.h> #include <linux/of.h> +#include <linux/regmap.h> #ifdef CONFIG_COMMON_CLK @@ -31,6 +32,7 @@ #define CLK_SET_RATE_NO_REPARENT BIT(7) /* don't re-parent on rate change */ #define CLK_GET_ACCURACY_NOCACHE BIT(8) /* do not use the cached clk accuracy */ #define CLK_RECALC_NEW_RATES BIT(9) /* recalc rates after notifications */ +#define CLK_USE_REGMAP BIT(10) /* uses regmap to access registers */ struct clk; struct clk_hw; @@ -290,6 +292,8 @@ void of_fixed_clk_setup(struct device_node *np); * * @hw: handle between common and hardware-specific interfaces * @reg: register controlling gate + * @regmap: regmap used to control the gate + * @offset: offset inside the regmap * @bit_idx: single bit controlling gate * @flags: hardware-specific flags * @lock: register lock @@ -307,7 +311,11 @@ void of_fixed_clk_setup(struct device_node *np); */ struct clk_gate { struct clk_hw hw; - void __iomem *reg; + union { + void __iomem *reg; + struct regmap *regmap; + }; + u32 offset; u8 bit_idx; u8 flags; spinlock_t *lock; @@ -323,6 +331,11 @@ struct clk *clk_register_gate(struct device *dev, const char *name, u8 clk_gate_flags, spinlock_t *lock); void clk_unregister_gate(struct clk *clk); +struct clk *clk_regm_register_gate(struct device *dev, const char *name, + const char *parent_name, unsigned long flags, + struct regmap *regmap, u32 offset, u8 bit_idx, + u8 clk_gate_flags, spinlock_t *lock); + struct clk_div_table { unsigned int val; unsigned int div; @@ -333,6 +346,8 @@ struct clk_div_table { * * @hw: handle between common and hardware-specific interfaces * @reg: register containing the divider + * @regmap: regmap used to access the divider + * @offest: offset inside the regmap * @shift: shift to the divider bit field * @width: width of the divider bit field * @table: array of value/divider pairs, last entry should have div = 0 @@ -367,7 +382,11 @@ struct clk_div_table { */ struct clk_divider { struct clk_hw hw; - void __iomem *reg; + union { + void __iomem *reg; + struct regmap *regmap; + }; + u32 offset; u8 shift; u8 width; u8 flags; @@ -406,11 +425,24 @@ struct clk *clk_register_divider_table(struct device *dev, const char *name, spinlock_t *lock); void clk_unregister_divider(struct clk *clk); +struct clk *clk_regm_register_divider(struct device *dev, const char *name, + const char *parent_name, unsigned long flags, + struct regmap *regmap, u32 offset, u8 shift, u8 width, + u8 clk_divider_flags, spinlock_t *lock); + +struct clk *clk_regm_register_divider_table(struct device *dev, + const char *name, const char *parent_name, unsigned long flags, + struct regmap *regmap, u32 offset, u8 shift, u8 width, + u8 clk_divider_flags, const struct clk_div_table *table, + spinlock_t *lock); + /** * struct clk_mux - multiplexer clock * * @hw: handle between common and hardware-specific interfaces * @reg: register controlling multiplexer + * @regmap: regmap for controlling multiplexer + * @offset: offset inside the regmap * @shift: shift to multiplexer bit field * @width: width of mutliplexer bit field * @flags: hardware-specific flags @@ -431,8 +463,12 @@ void clk_unregister_divider(struct clk *clk); */ struct clk_mux { struct clk_hw hw; - void __iomem *reg; + union { + void __iomem *reg; + struct regmap *regmap; + }; u32 *table; + u32 offset; u32 mask; u8 shift; u8 flags; @@ -462,6 +498,18 @@ struct clk *clk_register_mux_table(struct device *dev, const char *name, void clk_unregister_mux(struct clk *clk); +struct clk *clk_regm_register_mux_table(struct device *dev, const char *name, + const char * const *parent_names, u8 num_parents, + unsigned long flags, struct regmap *regmap, + u32 offset, u8 shift, u32 mask, + u8 clk_mux_flags, u32 *table, spinlock_t *lock); + +struct clk *clk_regm_register_mux(struct device *dev, const char *name, + const char * const *parent_names, u8 num_parents, + unsigned long flags, struct regmap *regmap, + u32 offset, u8 shift, u8 width, + u8 clk_mux_flags, spinlock_t *lock); + void of_fixed_factor_clk_setup(struct device_node *node); /** -- 2.6.4 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html