Em 08-11-2011 21:54, Antti Palosaari escreveu:
> Function that splits and sends most typical I2C register write.
>
> Signed-off-by: Antti Palosaari <crope@xxxxxx>
> ---
> drivers/media/dvb/dvb-core/Makefile | 2 +-
> drivers/media/dvb/dvb-core/dvb_generic.c | 48 ++++++++++++++++++++++++++++++
> drivers/media/dvb/dvb-core/dvb_generic.h | 21 +++++++++++++
> 3 files changed, 70 insertions(+), 1 deletions(-)
> create mode 100644 drivers/media/dvb/dvb-core/dvb_generic.c
> create mode 100644 drivers/media/dvb/dvb-core/dvb_generic.h
>
> diff --git a/drivers/media/dvb/dvb-core/Makefile b/drivers/media/dvb/dvb-core/Makefile
> index 8f22bcd..230584a 100644
> --- a/drivers/media/dvb/dvb-core/Makefile
> +++ b/drivers/media/dvb/dvb-core/Makefile
> @@ -6,6 +6,6 @@ dvb-net-$(CONFIG_DVB_NET) := dvb_net.o
>
> dvb-core-objs := dvbdev.o dmxdev.o dvb_demux.o dvb_filter.o \
> dvb_ca_en50221.o dvb_frontend.o \
> - $(dvb-net-y) dvb_ringbuffer.o dvb_math.o
> + $(dvb-net-y) dvb_ringbuffer.o dvb_math.o dvb_generic.o
>
> obj-$(CONFIG_DVB_CORE) += dvb-core.o
> diff --git a/drivers/media/dvb/dvb-core/dvb_generic.c b/drivers/media/dvb/dvb-core/dvb_generic.c
> new file mode 100644
> index 0000000..002bd24
> --- /dev/null
> +++ b/drivers/media/dvb/dvb-core/dvb_generic.c
> @@ -0,0 +1,48 @@
> +#include <linux/i2c.h>
> +#include "dvb_generic.h"
> +
> +/* write multiple registers */
> +int dvb_wr_regs(struct dvb_i2c_cfg *i2c_cfg, u8 reg, u8 *val, int len_tot)
> +{
> +#define REG_ADDR_LEN 1
> +#define REG_VAL_LEN 1
> + int ret, len_cur, len_rem, len_max;
> + u8 buf[i2c_cfg->max_wr];
> + struct i2c_msg msg[1] = {
> + {
> + .addr = i2c_cfg->addr,
> + .flags = 0,
> + .buf = buf,
> + }
> + };
> +
> + len_max = i2c_cfg->max_wr - REG_ADDR_LEN;
> + for (len_rem = len_tot; len_rem > 0; len_rem -= len_max) {
> + len_cur = len_rem;
> + if (len_cur > len_max)
> + len_cur = len_max;
> +
> + msg[0].len = len_cur + REG_ADDR_LEN;
> + buf[0] = reg;
> + memcpy(&buf[REG_ADDR_LEN], &val[len_tot - len_rem], len_cur);
> +
> + ret = i2c_transfer(i2c_cfg->adapter, msg, 1);
> + if (ret != 1) {
> + warn("i2c wr failed=%d reg=%02x len=%d",
> + ret, reg, len_cur);
> + return -EREMOTEIO;
> + }
Due to the way I2C locks are bound, doing something like the above and something like:
struct i2c_msg msg[2] = {
{
.addr = i2c_cfg->addr,
.flags = 0,
.buf = buf,
},
{
.addr = i2c_cfg->addr,
.flags = 0,
.buf = buf2,
}
};
ret = i2c_transfer(i2c_cfg->adapter, msg, 2);
Produces a different result. In the latter case, I2C core avoids having any other
transaction in the middle of the 2 messages.
I like the idea of having some functions to help handling those cases where a single
transaction needs to be split into several messages.
Yet, I agree with Michael: I would add such logic inside the I2C subsystem, and
being sure that the lock is kept during the entire I2C operation.
Jean,
Thoughts?
> + reg += len_cur;
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(dvb_wr_regs);
> +
> +/* write single register */
> +int dvb_wr_reg(struct dvb_i2c_cfg *i2c_cfg, u8 reg, u8 val)
> +{
> + return dvb_wr_regs(i2c_cfg, reg, &val, 1);
> +}
> +EXPORT_SYMBOL(dvb_wr_reg);
> +
> diff --git a/drivers/media/dvb/dvb-core/dvb_generic.h b/drivers/media/dvb/dvb-core/dvb_generic.h
> new file mode 100644
> index 0000000..7a140ab
> --- /dev/null
> +++ b/drivers/media/dvb/dvb-core/dvb_generic.h
> @@ -0,0 +1,21 @@
> +#ifndef DVB_GENERIC_H
> +#define DVB_GENERIC_H
> +
> +#define DVB_GENERIC_LOG_PREFIX "dvb_generic"
> +#define warn(f, arg...) \
> + printk(KERN_WARNING DVB_GENERIC_LOG_PREFIX": " f "\n", ## arg)
> +
> +struct dvb_i2c_cfg {
> + struct i2c_adapter *adapter;
> + u8 addr;
> + /* TODO: reg_addr_len; as now use one byte */
> + /* TODO: reg_val_len; as now use one byte */
> + u8 max_wr;
> + u8 max_rd;
> +};
> +
> +extern int dvb_wr_regs(struct dvb_i2c_cfg *, u8, u8 *, int);
> +extern int dvb_wr_reg(struct dvb_i2c_cfg *, u8, u8);
> +
> +#endif
> +
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