* [PATCH 2/3 v2] at24: Support SMBus byte writes to 16-bit devices
2015-09-03 19:53 ` [PATCH 2/3] at24: Support SMBus byte writes to 16-bit devices Aaron Sierra
@ 2015-09-21 18:39 ` Aaron Sierra
2015-11-03 8:43 ` [PATCH 2/3] " Jean Delvare
1 sibling, 0 replies; 3+ messages in thread
From: Aaron Sierra @ 2015-09-21 18:39 UTC (permalink / raw)
To: Wolfram Sang; +Cc: linux-i2c, Christian Gmeiner, Jean Delvare, Nate Case
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@xes-inc.com>
Signed-off-by: Aaron Sierra <asierra@xes-inc.com>
---
v2 - Unchanged from v1
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 c3d3add..32eca05 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),
+ (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,
@@ -376,8 +395,8 @@ 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;
}
@@ -562,7 +581,17 @@ 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 &&
+ i2c_check_functionality(client->adapter,
+ I2C_FUNC_SMBUS_WRITE_WORD_DATA)) {
+ /*
+ * 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;
--
1.9.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH 2/3] at24: Support SMBus byte writes to 16-bit devices
2015-09-03 19:53 ` [PATCH 2/3] at24: Support SMBus byte writes to 16-bit devices Aaron Sierra
2015-09-21 18:39 ` [PATCH 2/3 v2] " Aaron Sierra
@ 2015-11-03 8:43 ` Jean Delvare
1 sibling, 0 replies; 3+ messages in thread
From: Jean Delvare @ 2015-11-03 8:43 UTC (permalink / raw)
To: Aaron Sierra; +Cc: Wolfram Sang, linux-i2c, Christian Gmeiner
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@xes-inc.com>
> Signed-off-by: Aaron Sierra <asierra@xes-inc.com>
> ---
> 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
^ permalink raw reply [flat|nested] 3+ messages in thread