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Date: Tue, 12 Nov 2019 10:59:30 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
CC: Wolfram Sang <wsa@...-dreams.de>,
Jonathan Cameron <jic23@...nel.org>,
Hartmut Knaack <knaack.h@....de>,
Lars-Peter Clausen <lars@...afoo.de>,
"Peter Meerwald-Stadler" <pmeerw@...erw.net>,
<linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-iio@...r.kernel.org>
Subject: Re: [PATCH v2] i2c: use void pointers for supplying data for reads
and writes
On Mon, 11 Nov 2019 16:58:26 -0800
Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> There is no need to force users of i2c_master_send()/i2c_master_recv()
> and other i2c read/write bulk data API to cast everything into u8
> pointers. While everything can be considered byte stream, the drivers
> are usually work with more structured data.
>
> Let's switch the APIs to accept [const] void pointers to cut amount of
> casting needed.
>
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> ---
>
> Changes in v2:
>
> - adjusted max1363 to the new i2c_master_send/recv signatures
>
> I sent the previous version of this patch 04/01/17 and kbuild promptly
> noticed that it broke max1363. And it took me only 2.5 years to get back
> to it ;)
>
> Given that it is only one IIO driver that is affected I hope it can go
> through Wolfram's tree and we do not need to go through staged API
> rollout.
>
> drivers/i2c/i2c-core-base.c | 2 +-
> drivers/i2c/i2c-core-smbus.c | 16 ++++++++--------
> drivers/iio/adc/max1363.c | 14 ++++++++------
> include/linux/i2c.h | 28 +++++++++++++++-------------
> 4 files changed, 32 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index 6a5183cffdfc3..aeb4201ef55e4 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -2065,7 +2065,7 @@ EXPORT_SYMBOL(i2c_transfer);
> *
> * Returns negative errno, or else the number of bytes transferred.
> */
> -int i2c_transfer_buffer_flags(const struct i2c_client *client, char *buf,
> +int i2c_transfer_buffer_flags(const struct i2c_client *client, void *buf,
> int count, u16 flags)
> {
> int ret;
> diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
> index 3ac426a8ab5ab..4172f8e647f81 100644
> --- a/drivers/i2c/i2c-core-smbus.c
> +++ b/drivers/i2c/i2c-core-smbus.c
> @@ -15,6 +15,7 @@
> #include <linux/i2c.h>
> #include <linux/i2c-smbus.h>
> #include <linux/slab.h>
> +#include <asm/unaligned.h>
>
> #include "i2c-core.h"
>
> @@ -213,7 +214,7 @@ EXPORT_SYMBOL(i2c_smbus_write_word_data);
> * mechanism (I2C_M_RECV_LEN) which may not be implemented.
> */
> s32 i2c_smbus_read_block_data(const struct i2c_client *client, u8 command,
> - u8 *values)
> + void *values)
> {
> union i2c_smbus_data data;
> int status;
> @@ -240,7 +241,7 @@ EXPORT_SYMBOL(i2c_smbus_read_block_data);
> * else zero on success.
> */
> s32 i2c_smbus_write_block_data(const struct i2c_client *client, u8 command,
> - u8 length, const u8 *values)
> + u8 length, const void *values)
> {
> union i2c_smbus_data data;
>
> @@ -256,7 +257,7 @@ EXPORT_SYMBOL(i2c_smbus_write_block_data);
>
> /* Returns the number of read bytes */
> s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, u8 command,
> - u8 length, u8 *values)
> + u8 length, void *values)
> {
> union i2c_smbus_data data;
> int status;
> @@ -276,7 +277,7 @@ s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, u8 command,
> EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data);
>
> s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, u8 command,
> - u8 length, const u8 *values)
> + u8 length, const void *values)
> {
> union i2c_smbus_data data;
>
> @@ -628,7 +629,7 @@ EXPORT_SYMBOL(__i2c_smbus_xfer);
> * transfer.
> */
> s32 i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client,
> - u8 command, u8 length, u8 *values)
> + u8 command, u8 length, void *values)
> {
> u8 i = 0;
> int status;
> @@ -647,8 +648,7 @@ s32 i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client,
> status = i2c_smbus_read_word_data(client, command + i);
> if (status < 0)
> return status;
> - values[i] = status & 0xff;
> - values[i + 1] = status >> 8;
> + put_unaligned_le16(status, values + i);
> i += 2;
> }
> }
> @@ -657,7 +657,7 @@ s32 i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client,
> status = i2c_smbus_read_byte_data(client, command + i);
> if (status < 0)
> return status;
> - values[i] = status;
> + *(u8 *)(values + i) = status;
> i++;
> }
>
> diff --git a/drivers/iio/adc/max1363.c b/drivers/iio/adc/max1363.c
> index 5c2cc61b666e7..48ed76a0e83d4 100644
> --- a/drivers/iio/adc/max1363.c
> +++ b/drivers/iio/adc/max1363.c
> @@ -182,9 +182,9 @@ struct max1363_state {
> struct regulator *vref;
> u32 vref_uv;
> int (*send)(const struct i2c_client *client,
> - const char *buf, int count);
> + const void *buf, int count);
> int (*recv)(const struct i2c_client *client,
> - char *buf, int count);
> + void *buf, int count);
> };
>
> #define MAX1363_MODE_SINGLE(_num, _mask) { \
> @@ -310,27 +310,29 @@ static const struct max1363_mode
> return NULL;
> }
>
> -static int max1363_smbus_send(const struct i2c_client *client, const char *buf,
> +static int max1363_smbus_send(const struct i2c_client *client, const void *buf,
> int count)
> {
> + const u8 *data = buf;
> int i, err;
>
> for (i = err = 0; err == 0 && i < count; ++i)
> - err = i2c_smbus_write_byte(client, buf[i]);
> + err = i2c_smbus_write_byte(client, data[i]);
>
> return err ? err : count;
> }
>
> -static int max1363_smbus_recv(const struct i2c_client *client, char *buf,
> +static int max1363_smbus_recv(const struct i2c_client *client, void *buf,
> int count)
> {
> + u8 *data = buf;
> int i, ret;
>
> for (i = 0; i < count; ++i) {
> ret = i2c_smbus_read_byte(client);
> if (ret < 0)
> return ret;
> - buf[i] = ret;
> + data[i] = ret;
> }
>
> return count;
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index aaf57d9b41dbb..64cf92e191aa8 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -51,7 +51,7 @@ struct property_entry;
> * @count must be be less than 64k since msg.len is u16.
> */
> extern int i2c_transfer_buffer_flags(const struct i2c_client *client,
> - char *buf, int count, u16 flags);
> + void *buf, int count, u16 flags);
>
> /**
> * i2c_master_recv - issue a single I2C message in master receive mode
> @@ -62,7 +62,7 @@ extern int i2c_transfer_buffer_flags(const struct i2c_client *client,
> * Returns negative errno, or else the number of bytes read.
> */
> static inline int i2c_master_recv(const struct i2c_client *client,
> - char *buf, int count)
> + void *buf, int count)
> {
> return i2c_transfer_buffer_flags(client, buf, count, I2C_M_RD);
> };
> @@ -77,7 +77,7 @@ static inline int i2c_master_recv(const struct i2c_client *client,
> * Returns negative errno, or else the number of bytes read.
> */
> static inline int i2c_master_recv_dmasafe(const struct i2c_client *client,
> - char *buf, int count)
> + void *buf, int count)
> {
> return i2c_transfer_buffer_flags(client, buf, count,
> I2C_M_RD | I2C_M_DMA_SAFE);
> @@ -92,9 +92,10 @@ static inline int i2c_master_recv_dmasafe(const struct i2c_client *client,
> * Returns negative errno, or else the number of bytes written.
> */
> static inline int i2c_master_send(const struct i2c_client *client,
> - const char *buf, int count)
> + const void *buf, int count)
> {
> - return i2c_transfer_buffer_flags(client, (char *)buf, count, 0);
> + return i2c_transfer_buffer_flags(client, (void *)buf /* const cast */,
> + count, 0);
> };
>
> /**
> @@ -107,10 +108,10 @@ static inline int i2c_master_send(const struct i2c_client *client,
> * Returns negative errno, or else the number of bytes written.
> */
> static inline int i2c_master_send_dmasafe(const struct i2c_client *client,
> - const char *buf, int count)
> + const void *buf, int count)
> {
> - return i2c_transfer_buffer_flags(client, (char *)buf, count,
> - I2C_M_DMA_SAFE);
> + return i2c_transfer_buffer_flags(client, (void *)buf /* const cast */,
> + count, I2C_M_DMA_SAFE);
> };
>
> /* Transfer num messages.
> @@ -166,18 +167,19 @@ i2c_smbus_write_word_swapped(const struct i2c_client *client,
>
> /* Returns the number of read bytes */
> extern s32 i2c_smbus_read_block_data(const struct i2c_client *client,
> - u8 command, u8 *values);
> + u8 command, void *values);
> extern s32 i2c_smbus_write_block_data(const struct i2c_client *client,
> - u8 command, u8 length, const u8 *values);
> + u8 command, u8 length,
> + const void *values);
> /* Returns the number of read bytes */
> extern s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client,
> - u8 command, u8 length, u8 *values);
> + u8 command, u8 length, void *values);
> extern s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client,
> u8 command, u8 length,
> - const u8 *values);
> + const void *values);
> extern s32
> i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client,
> - u8 command, u8 length, u8 *values);
> + u8 command, u8 length, void *values);
> int i2c_get_device_id(const struct i2c_client *client,
> struct i2c_device_identity *id);
> #endif /* I2C */
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