On Thu, 3 Sep 2015 14:53:18 -0500 (CDT), Aaron Sierra wrote:
> Introduce at24_smbus_write_byte_data() to allow very slow (e.g.
> 248 B/s) write access to 16-bit EEPROM devices attached to SMBus
> controllers like the Intel SCH.
>
> Signed-off-by: Nate Case <ncase@xxxxxxxxxxx>
> Signed-off-by: Aaron Sierra <asierra@xxxxxxxxxxx>
> ---
> drivers/misc/eeprom/at24.c | 35 ++++++++++++++++++++++++++++++++---
> 1 file changed, 32 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index 4cf53a0..2ee1301 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -134,6 +134,25 @@ MODULE_DEVICE_TABLE(i2c, at24_ids);
> /*-------------------------------------------------------------------------*/
>
> /*
> + * Write a byte to an AT24 device using SMBus cycles.
> + */
> +static inline s32 at24_smbus_write_byte_data(struct at24_data *at24,
> + struct i2c_client *client, u16 offset, u8 value)
> +{
> + if (!(at24->chip.flags & AT24_FLAG_ADDR16))
> + return i2c_smbus_write_byte_data(client, offset, value);
> +
> + /*
> + * Emulate I2C multi-byte write by using SMBus "write word"
> + * cycle. We split up the 16-bit offset among the "command"
> + * byte and the first data byte.
> + */
> + return i2c_smbus_write_word_data(client,
> + ((offset >> 8) & 0xff),
Useless masking.
> + (value << 8) | (offset & 0xff));
> +}
> +
> +/*
> * Write block data to an AT24 device using SMBus cycles.
> */
> static inline s32 at24_smbus_write_i2c_block_data(struct at24_data *at24,
> @@ -401,8 +420,8 @@ static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
> client, offset, count, buf);
> break;
> case I2C_SMBUS_BYTE_DATA:
> - status = i2c_smbus_write_byte_data(client,
> - offset, buf[0]);
> + status = at24_smbus_write_byte_data(at24,
> + client, offset, buf[0]);
> break;
> }
>
> @@ -590,7 +609,17 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
> if (i2c_check_functionality(client->adapter,
> I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
> use_smbus_write = I2C_SMBUS_I2C_BLOCK_DATA;
> - } else if (i2c_check_functionality(client->adapter,
> + } else if (chip.flags & AT24_FLAG_ADDR16 &&
Parentheses around (x & y) please.
> + i2c_check_functionality(client->adapter,
> + I2C_FUNC_SMBUS_WRITE_WORD_DATA)) {
Would be good to align this the same way the other two are aligned.
> + /*
> + * We need SMBUS_WRITE_WORD_DATA to implement
> + * byte writes for 16-bit address devices.
> + */
> + use_smbus_write = I2C_SMBUS_BYTE_DATA;
> + chip.page_size = 1;
> + } else if (!(chip.flags & AT24_FLAG_ADDR16) &&
> + i2c_check_functionality(client->adapter,
> I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
> use_smbus_write = I2C_SMBUS_BYTE_DATA;
> chip.page_size = 1;
Like patch 1/3, the code you are adding in this patch can't be tested.
--
Jean Delvare
SUSE L3 Support
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