Dear Daniel, On Wed, 18 Mar 2015 12:24:40 +0000 Daniel Stone <daniel@xxxxxxxxxxxxx> wrote: > Hi, > Some feedback comments - most of these are not unique to your 5433 > DECON driver but endemic throughout Exynos, so I don't blame you for > them - but they should be fixed anyway. > > On 18 March 2015 at 08:16, Hyungwon Hwang <human.hwang@xxxxxxxxxxx> > wrote: > > +static void decon_dpms_on(struct exynos_decon *decon) > > +{ > > + int ret; > > + int i; > > + > > + for (i = 0; i < ARRAY_SIZE(decon_clks_name); i++) { > > + ret = clk_prepare_enable(decon->clks[i]); > > + if (ret < 0) > > + goto err; > > + } > > + > > + set_bit(BIT_CLKS_ENABLED, &decon->enabled); > > Do you really not even need to set a control register? > > > +static void decon_commit(struct exynos_drm_crtc *crtc) > > +{ > > + struct exynos_decon *decon = crtc->ctx; > > + struct drm_display_mode *mode = &crtc->base.mode; > > + u32 val; > > + > > + /* enable clock gate */ > > + val = CMU_CLKGAGE_MODE_SFR_F | CMU_CLKGAGE_MODE_MEM_F; > > + writel(val, decon->addr + DECON_CMU); > > + > > + /* lcd on and use command if */ > > + val = VIDOUT_LCD_ON; > > + if (decon->i80_if) > > + val |= VIDOUT_COMMAND_IF; > > + else > > + val |= VIDOUT_RGB_IF; > > + writel(val, decon->addr + DECON_VIDOUTCON0); > > This seems much more likely to be DPMS, no? > > > + [...] > > + /* enable output and display signal */ > > + val = VIDCON0_ENVID | VIDCON0_ENVID_F; > > + writel(val, decon->addr + DECON_VIDCON0); > > As does this. > > Have you tested DPMS on/off, without enabling/disabling the CRTC > first? Does it work? Yes. I misunderstanded the behavior of the driver. I will send the fixed version for working DPMS. Thanks. > > > +static void decon_win_mode_set(struct exynos_drm_crtc *crtc, > > + struct exynos_drm_plane *plane) > > +{ > > + struct exynos_decon *decon = crtc->ctx; > > + struct decon_reg_data *reg_data; > > + unsigned int bytes_per_pixel = plane->bpp >> 3; > > + unsigned int val_h; > > + unsigned int val_l; > > + unsigned int win; > > + dma_addr_t addr; > > + u32 val = 0; > > + > > + if (!plane) { > > + DRM_ERROR("plane is NULL\n"); > > + return; > > + } > > + > > + win = plane->zpos; > > + if (win == DEFAULT_ZPOS) > > + win = 0; > > + > > + if (win < 0 || win >= 5) > > + return; > > It would be nice to have a #define for the largest-supported window > number. Yes. That would be better. > > > + reg_data = &decon->reg_data[win]; > > + > > + switch (plane->pixel_format) { > > + case DRM_FORMAT_XRGB1555: > > + val |= WINCONx_BPPMODE_16BPP_I1555; > > + val |= WINCONx_HAWSWP_F; > > + val |= WINCONx_BURSTLEN_16WORD; > > + break; > > + case DRM_FORMAT_RGB565: > > + val |= WINCONx_BPPMODE_16BPP_565; > > + val |= WINCONx_HAWSWP_F; > > + val |= WINCONx_BURSTLEN_16WORD; > > + break; > > + case DRM_FORMAT_XRGB8888: > > + val |= WINCONx_BPPMODE_24BPP_888; > > + val |= WINCONx_WSWP_F; > > + val |= WINCONx_BURSTLEN_16WORD; > > + break; > > + case DRM_FORMAT_ARGB8888: > > + val |= WINCONx_BPPMODE_32BPP_A8888; > > + val |= WINCONx_WSWP_F | WINCONx_BLD_PIX_F | > > WINCONx_ALPHA_SEL_F; > > + val |= WINCONx_BURSTLEN_16WORD; > > + break; > > + default: > > Please remove the 'default' case. If you get here with a format you > don't know how to configure, then it is a bug and should be fixed: the > plane should never advertise a format that it cannot support. > Yes. I agree. > > + val |= WINCONx_BPPMODE_24BPP_888; > > + val |= WINCONx_WSWP_F; > > + val |= WINCONx_BURSTLEN_16WORD; > > + break; > > + } > > + > > + reg_data->wincon = val; > > + reg_data->vidosd_a = COORDINATE_X(plane->crtc_x) | > > + COORDINATE_Y(plane->crtc_y); > > + reg_data->vidosd_b = > > + COORDINATE_X(plane->crtc_x + plane->crtc_width - 1) > > | > > + COORDINATE_Y(plane->crtc_y + plane->crtc_height - > > 1); > > + reg_data->vidosd_c = VIDOSD_Wx_ALPHA_R_F(0x0) | > > + VIDOSD_Wx_ALPHA_G_F(0x0) | > > + VIDOSD_Wx_ALPHA_B_F(0x0); > > + reg_data->vidosd_d = VIDOSD_Wx_ALPHA_R_F(0x0) | > > + VIDOSD_Wx_ALPHA_G_F(0x0) | > > + VIDOSD_Wx_ALPHA_B_F(0x0); > > + > > + addr = plane->dma_addr[0]; > > + addr += plane->fb_width * plane->fb_y * bytes_per_pixel; > > Replace plane->fb_width * bytes_per_pixel by plane->fb_pitch please, > and set plane->fb_pitch from exynos_drm_plane->pitch. See this patch: > https://www.mail-archive.com/linux-samsung-soc@xxxxxxxxxxxxxxx/msg42861.html > > You should be able to test this case, either by making a specialised > userspace program which has a larger pitch with garbage values in the > padding (see > https://msdn.microsoft.com/en-us/library/windows/desktop/aa473780(v=vs.85).aspx), > or by testing a resolution where width*bytespp is not a multiple of > 4, e.g. 1366x768. > Yes. I agree. > > + addr += plane->fb_x * bytes_per_pixel; > > + > > + reg_data->vidw_add0 = addr; > > + > > + addr += plane->fb_width * plane->crtc_height * > > bytes_per_pixel; > > Again, replace fb_width*bytes_per_pixel with fb_pitch. > > > + reg_data->vidw_add1 = addr; > > + > > + val_h = (plane->fb_width - plane->crtc_width) * > > bytes_per_pixel; > > val_h = plane->fb_pitch - (plane->crtc_width * bytes_per_pixel); > > > +static void decon_win_commit(struct exynos_drm_crtc *crtc, int > > zpos) +{ > > + struct exynos_decon *decon = crtc->ctx; > > + struct decon_reg_data *reg_data; > > + unsigned int win = zpos; > > + u32 val; > > + > > + if (win == DEFAULT_ZPOS) > > + win = 0; > > + > > + if (win < 0 || win >= 5) > > + return; > > + > > + reg_data = &decon->reg_data[win]; > > + > > + /* shadow update disable */ > > + val = readl(decon->addr + DECON_SHADOWCON); > > + val |= SHADOWCON_Wx_PROTECT(win); > > + writel(val, decon->addr + DECON_SHADOWCON); > > + > > + writel(reg_data->vidosd_a, decon->addr + > > DECON_VIDOSDxA(win)); > > + writel(reg_data->vidosd_b, decon->addr + > > DECON_VIDOSDxB(win)); > > + writel(reg_data->vidosd_c, decon->addr + > > DECON_VIDOSDxC(win)); > > + writel(reg_data->vidosd_d, decon->addr + > > DECON_VIDOSDxD(win)); > > + writel(reg_data->vidw_add0, decon->addr + > > DECON_VIDW0xADD0B0(win)); > > + writel(reg_data->vidw_add1, decon->addr + > > DECON_VIDW0xADD1B0(win)); > > + writel(reg_data->vidw_add2, decon->addr + > > DECON_VIDW0xADD2(win)); + > > + /* window enable */ > > + val = reg_data->wincon; > > + val |= WINCONx_ENWIN_F; > > + writel(val, decon->addr + DECON_WINCONx(win)); > > + > > + /* shadow update enable */ > > + val = readl(decon->addr + DECON_SHADOWCON); > > + val &= ~SHADOWCON_Wx_PROTECT(win); > > + writel(val, decon->addr + DECON_SHADOWCON); > > + > > + /* standalone update */ > > + val = readl(decon->addr + DECON_UPDATE); > > + val |= STANDALONE_UPDATE_F; > > + writel(val, decon->addr + DECON_UPDATE); > > + > > + if (decon->i80_if) > > + atomic_set(&decon->win_updated, 1); > > +} > > + > > +static void decon_win_disable(struct exynos_drm_crtc *crtc, int > > zpos) +{ > > + struct exynos_decon *decon = crtc->ctx; > > + struct decon_reg_data *reg_data; > > + unsigned int win = zpos; > > + u32 val; > > + > > + if (win == DEFAULT_ZPOS) > > + win = 0; > > + > > + if (win < 0 || win >= 5) > > + return; > > + > > + reg_data = &decon->reg_data[win]; > > + > > + /* shadow update disable */ > > + val = readl(decon->addr + DECON_SHADOWCON); > > + val |= SHADOWCON_Wx_PROTECT(win); > > + writel(val, decon->addr + DECON_SHADOWCON); > > + > > + /* window disable */ > > + val = reg_data->wincon; > > + val &= ~WINCONx_ENWIN_F; > > + writel(val, decon->addr + DECON_WINCONx(win)); > > + > > + /* shadow update enable */ > > + val = readl(decon->addr + DECON_SHADOWCON); > > + val &= ~SHADOWCON_Wx_PROTECT(win); > > + writel(val, decon->addr + DECON_SHADOWCON); > > + > > + /* standalone update */ > > + val = readl(decon->addr + DECON_UPDATE); > > + val |= STANDALONE_UPDATE_F; > > + writel(val, decon->addr + DECON_UPDATE); > > +} > > + > > +void decon_te_irq_handler(struct exynos_drm_crtc *crtc) > > +{ > > + struct exynos_decon *decon = crtc->ctx; > > + u32 val; > > + > > + if (!test_bit(BIT_CLKS_ENABLED, &decon->enabled)) > > + return; > > + > > + if (atomic_add_unless(&decon->win_updated, -1, 0)) { > > + /* trigger */ > > + val = readl(decon->addr + DECON_TRIGCON); > > + val |= TRIGCON_SWTRIGCMD; > > + writel(val, decon->addr + DECON_TRIGCON); > > + } > > +} > > + > > +static struct exynos_drm_crtc_ops decon_crtc_ops = { > > + .dpms = decon_dpms, > > + .enable_vblank = decon_enable_vblank, > > + .disable_vblank = decon_disable_vblank, > > + .commit = decon_commit, > > + .win_mode_set = decon_win_mode_set, > > + .win_commit = decon_win_commit, > > + .win_disable = decon_win_disable, > > + .te_handler = decon_te_irq_handler, > > +}; > > + > > +static int decon_bind(struct device *dev, struct device *master, > > void *data) +{ > > + struct exynos_decon *decon = dev_get_drvdata(dev); > > + struct drm_device *drm_dev = data; > > + struct exynos_drm_private *priv = drm_dev->dev_private; > > + > > + decon->drm_dev = drm_dev; > > + decon->pipe = priv->pipe++; > > + > > + decon->crtc = exynos_drm_crtc_create(drm_dev, decon->pipe, > > + EXYNOS_DISPLAY_TYPE_LCD, &decon_crtc_ops, > > decon); > > + if (IS_ERR(decon->crtc)) > > + return PTR_ERR(decon->crtc); > > Should failing to register the CRTC also decrement priv->pipe? > Yes. That's right. > > + > > + return 0; > > +} > > + > > +static void decon_unbind(struct device *dev, struct device > > *master, void *data) +{ > > + struct exynos_decon *decon = dev_get_drvdata(dev); > > + > > + decon_dpms(decon->crtc, DRM_MODE_DPMS_OFF); > > +} > > As above, it seems like DPMS will not do enough here. > > > +static const struct component_ops decon_component_ops = { > > + .bind = decon_bind, > > + .unbind = decon_unbind, > > +}; > > + > > +static irqreturn_t decon_vsync_irq_handler(int irq, void *dev_id) > > +{ > > + struct exynos_decon *decon = dev_id; > > + u32 val; > > + > > + if (!test_bit(BIT_CLKS_ENABLED, &decon->enabled)) > > + goto out; > > + > > + val = readl(decon->addr + DECON_VIDINTCON1); > > + if (val & VIDINTCON1_INTFRMPEND) { > > + if (decon->drm_dev) > > + drm_handle_vblank(decon->drm_dev, > > decon->pipe); > > If decon->drm_dev is ever NULL, it sounds like something has gone very > seriously wrong. decon->drm_dev will not be NULL at any time. So I will remove the if statement. > > > + /* clear */ > > + writel(VIDINTCON1_INTFRMPEND, decon->addr + > > DECON_VIDINTCON1); > > + } > > + > > +out: > > + return IRQ_HANDLED; > > +} > > + > > +static irqreturn_t decon_lcd_sys_irq_handler(int irq, void *dev_id) > > +{ > > + struct exynos_decon *decon = dev_id; > > + u32 val; > > + > > + if (!test_bit(BIT_CLKS_ENABLED, &decon->enabled)) > > + goto out; > > + > > + val = readl(decon->addr + DECON_VIDINTCON1); > > + if (val & VIDINTCON1_INTFRMDONEPEND) { > > + if (decon->drm_dev) > > + > > exynos_drm_crtc_finish_pageflip(decon->drm_dev, > > + > > decon->pipe); > > Ditto - when would drm_dev be NULL? Ditto. > > > + /* clear */ > > + writel(VIDINTCON1_INTFRMDONEPEND, > > + decon->addr + DECON_VIDINTCON1); > > + } > > + > > +out: > > + return IRQ_HANDLED; > > +} > > + > > +static int exynos5433_decon_probe(struct platform_device *pdev) > > +{ > > + struct device *dev = &pdev->dev; > > + struct exynos_decon *decon; > > + struct resource *res; > > + int ret; > > + int i; > > + > > + decon = devm_kzalloc(dev, sizeof(*decon), GFP_KERNEL); > > + if (!decon) > > + return -ENOMEM; > > + > > + decon->dev = dev; > > + if (of_get_child_by_name(dev->of_node, "i80-if-timings")) > > + decon->i80_if = true; > > + > > + for (i = 0; i < ARRAY_SIZE(decon_clks_name); i++) { > > + struct clk *clk; > > + > > + clk = devm_clk_get(decon->dev, decon_clks_name[i]); > > + if (IS_ERR(clk)) > > + return PTR_ERR(clk); > > + > > + decon->clks[i] = clk; > > + } > > + > > + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); > > + if (!res) { > > + dev_err(dev, "cannot find IO resource\n"); > > + return -ENXIO; > > + } > > + > > + decon->addr = devm_ioremap_resource(dev, res); > > + if (IS_ERR(decon->addr)) { > > + dev_err(dev, "ioremap failed\n"); > > + return PTR_ERR(decon->addr); > > + } > > + > > + res = platform_get_resource_byname(pdev, IORESOURCE_IRQ, > > + decon->i80_if ? "lcd_sys" : "vsync"); > > + if (!res) { > > + dev_err(dev, "cannot find IRQ resource\n"); > > + return -ENXIO; > > + } > > + > > + ret = devm_request_irq(dev, res->start, decon->i80_if ? > > + decon_lcd_sys_irq_handler : > > decon_vsync_irq_handler, 0, > > + "drm_decon", decon); > > + if (ret < 0) { > > + dev_err(dev, "lcd_sys irq request failed\n"); > > + return ret; > > + } > > + > > + ret = exynos_drm_component_add(dev, EXYNOS_DEVICE_TYPE_CRTC, > > + EXYNOS_DISPLAY_TYPE_LCD); > > + if (ret < 0) > > + return ret; > > + > > + platform_set_drvdata(pdev, decon); > > + > > + ret = component_add(dev, &decon_component_ops); > > + if (ret < 0) { > > + exynos_drm_component_del(dev, > > EXYNOS_DEVICE_TYPE_CRTC); > > + return ret; > > + } > > + > > + return 0; > > +} > > + > > +static int exynos5433_decon_remove(struct platform_device *pdev) > > +{ > > + component_del(&pdev->dev, &decon_component_ops); > > + exynos_drm_component_del(&pdev->dev, > > EXYNOS_DEVICE_TYPE_CRTC); + > > + return 0; > > +} > > + > > +static const struct of_device_id > > exynos5433_decon_driver_dt_match[] = { > > + { .compatible = "samsung,exynos5433-decon" }, > > + {}, > > +}; > > +MODULE_DEVICE_TABLE(of, exynos5433_decon_driver_dt_match); > > + > > +struct platform_driver exynos5433_decon_driver = { > > + .probe = exynos5433_decon_probe, > > + .remove = exynos5433_decon_remove, > > + .driver = { > > + .name = "exynos5433-decon", > > + .owner = THIS_MODULE, > > + .of_match_table = exynos5433_decon_driver_dt_match, > > + }, > > +}; > > diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.c > > b/drivers/gpu/drm/exynos/exynos_drm_drv.c index 98a239a..1fa0dd0 > > 100644 --- a/drivers/gpu/drm/exynos/exynos_drm_drv.c > > +++ b/drivers/gpu/drm/exynos/exynos_drm_drv.c > > @@ -556,6 +556,9 @@ static struct platform_driver *const > > exynos_drm_kms_drivers[] = { #ifdef CONFIG_DRM_EXYNOS_FIMD > > &fimd_driver, > > #endif > > +#ifdef CONFIG_DRM_EXYNOS5433_DECON > > + &exynos5433_decon_driver, > > +#endif > > #ifdef CONFIG_DRM_EXYNOS7_DECON > > &decon_driver, > > #endif > > diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.h > > b/drivers/gpu/drm/exynos/exynos_drm_drv.h index 9afd390..40996d8 > > 100644 --- a/drivers/gpu/drm/exynos/exynos_drm_drv.h > > +++ b/drivers/gpu/drm/exynos/exynos_drm_drv.h > > @@ -344,6 +344,7 @@ void exynos_drm_component_del(struct device > > *dev, enum exynos_drm_device_type dev_type); > > > > extern struct platform_driver fimd_driver; > > +extern struct platform_driver exynos5433_decon_driver; > > extern struct platform_driver decon_driver; > > extern struct platform_driver dp_driver; > > extern struct platform_driver dsi_driver; > > diff --git a/drivers/gpu/drm/exynos/regs-exynos5433-decon.h > > b/drivers/gpu/drm/exynos/regs-exynos5433-decon.h new file mode > > 100644 index 0000000..9e7f851 > > --- /dev/null > > +++ b/drivers/gpu/drm/exynos/regs-exynos5433-decon.h > > @@ -0,0 +1,163 @@ > > +/* > > + * Copyright (C) 2014 Samsung Electronics Co.Ltd > > + * > > + * 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 Foundationr > > + */ > > + > > +#ifndef EXYNOS_REGS_DECON_H > > +#define EXYNOS_REGS_DECON_H > > + > > +/* Exynos543X DECON */ > > +#define DECON_VIDCON0 0x0000 > > +#define DECON_VIDOUTCON0 0x0010 > > +#define DECON_WINCONx(n) (0x0020 + ((n) * 4)) > > +#define DECON_VIDOSDxH(n) (0x0080 + ((n) * 4)) > > +#define DECON_SHADOWCON 0x00A0 > > +#define DECON_VIDOSDxA(n) (0x00B0 + ((n) * 0x20)) > > +#define DECON_VIDOSDxB(n) (0x00B4 + ((n) * 0x20)) > > +#define DECON_VIDOSDxC(n) (0x00B8 + ((n) * 0x20)) > > +#define DECON_VIDOSDxD(n) (0x00BC + ((n) * 0x20)) > > +#define DECON_VIDOSDxE(n) (0x00C0 + ((n) * 0x20)) > > +#define DECON_VIDW0xADD0B0(n) (0x0150 + ((n) * 0x10)) > > +#define DECON_VIDW0xADD0B1(n) (0x0154 + ((n) * 0x10)) > > +#define DECON_VIDW0xADD0B2(n) (0x0158 + ((n) * 0x10)) > > +#define DECON_VIDW0xADD1B0(n) (0x01A0 + ((n) * 0x10)) > > +#define DECON_VIDW0xADD1B1(n) (0x01A4 + ((n) * 0x10)) > > +#define DECON_VIDW0xADD1B2(n) (0x01A8 + ((n) * 0x10)) > > +#define DECON_VIDW0xADD2(n) (0x0200 + ((n) * 4)) > > +#define DECON_LOCALxSIZE(n) (0x0214 + ((n) * > > 4))change-booting-mode.sh --update +#define > > DECON_VIDINTCON0 0x0220 +#define > > DECON_VIDINTCON1 0x0224 +#define > > DECON_WxKEYCON0(n) (0x0230 + ((n - 1) * 8)) +#define > > DECON_WxKEYCON1(n) (0x0234 + ((n - 1) * 8)) +#define > > DECON_WxKEYALPHA(n) (0x0250 + ((n - 1) * 4)) +#define > > DECON_WINxMAP(n) (0x0270 + ((n) * 4)) +#define > > DECON_QOSLUT07_00 0x02C0 +#define > > DECON_QOSLUT15_08 0x02C4 +#define > > DECON_QOSCTRL 0x02C8 +#define > > DECON_BLENDERQx(n) (0x0300 + ((n - 1) * 4)) +#define > > DECON_BLENDCON 0x0310 +#define > > DECON_OPE_VIDW0xADD0(n) (0x0400 + ((n) * 4)) > > +#define DECON_OPE_VIDW0xADD1(n) (0x0414 + ((n) * > > 4)) +#define DECON_FRAMEFIFO_REG7 0x051C +#define > > DECON_FRAMEFIFO_REG8 0x0520 +#define > > DECON_FRAMEFIFO_STATUS 0x0524 +#define > > DECON_CMU 0x1404 +#define > > DECON_UPDATE 0x1410 +#define > > DECON_UPDATE_SCHEME 0x1438 +#define > > DECON_VIDCON1 0x2000 +#define > > DECON_VIDCON2 0x2004 +#define > > DECON_VIDCON3 0x2008 +#define > > DECON_VIDCON4 0x200C +#define > > DECON_VIDTCON2 0x2028 +#define > > DECON_FRAME_SIZE 0x2038 +#define > > DECON_LINECNT_OP_THRESHOLD 0x203C +#define > > DECON_TRIGCON 0x2040 +#define > > DECON_TRIGSKIP 0x2050 +#define > > DECON_CRCRDATA 0x20B0 +#define > > DECON_CRCCTRL 0x20B4 + > > +/* Exynos5430 DECON */ > > +#define DECON_VIDTCON0 0x2020 > > +#define DECON_VIDTCON1 0x2024 > > + > > +/* Exynos5433 DECON */ > > +#define DECON_VIDTCON00 0x2010 > > +#define DECON_VIDTCON01 0x2014 > > +#define DECON_VIDTCON10 0x2018 > > +#define DECON_VIDTCON11 0x201C > > + > > +/* Exynos543X DECON Internal */ > > +#define DECON_W013DSTREOCON 0x0320 > > +#define DECON_W233DSTREOCON 0x0324 > > +#define DECON_FRAMEFIFO_REG0 0x0500 > > +#define DECON_ENHANCER_CTRL 0x2100 > > + > > +/* Exynos543X DECON TV */ > > +#define DECON_VCLKCON0 0x0014 > > +#define DECON_VIDINTCON2 0x0228 > > +#define DECON_VIDINTCON3 0x022C > > Yes, my impression was that DECON supported both internal and > external, i.e. would replace both FIMD/Mixer. This patch only supports > the internal interface: are you planning to add support for the > external/TV/HDMI interface as well? If so, how does this work with the > DT format you have defined? Should there maybe separate decon-int and > decon-tv subnodes, each of which create one CRTC? The Android tree > seems to rely on static configuration, but presumably we would need a > much more nuanced approach. > > If so, it seems like the first start would be to add a basic DECON > binding which covered the entire controller, and then as a next step > add support for decon-int as a subdevice of this. > As I know, they are physically different devices even though they have similar names and similar operations. If it is right, I am not sure that congregating them in one DT node is right. I really appreciate your review. Thanks. > Cheers, > Daniel > Best regards, Hyungwon Hwang -- 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