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| author | Matt Johnston <matt@codeconstruct.com.au> | 2021-11-15 05:49:21 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2021-11-15 17:11:24 +0300 |
| commit | 13cae4a104d2b7205696229ba85d34cc035f8c84 (patch) | |
| tree | 087813184352ae3f0f9788a737dfbc13c02f9b5a /include/linux | |
| parent | cc0be1ad686fb29a4d127948486f40b17fb34b50 (diff) | |
| download | linux-13cae4a104d2b7205696229ba85d34cc035f8c84.tar.xz | |
i2c: core: Allow 255 byte transfers for SMBus 3.x
SMBus 3.0 increased the maximum block transfer size from 32 bytes to
255 bytes. We increase the size of struct i2c_smbus_data's block[]
member.
i2c_smbus_xfer() and i2c_smbus_xfer_emulated() now support 255 byte
block operations, other block functions remain limited to 32 bytes for
compatibility with existing callers.
We allow adapters to indicate support for the larger size with
I2C_FUNC_SMBUS_V3_BLOCK. Most emulated drivers should be able to use 255
byte blocks by replacing I2C_SMBUS_BLOCK_MAX with I2C_SMBUS_V3_BLOCK_MAX
though some will have hardware limitations that need testing.
Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/i2c.h | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 16119ac1aa97..353d6b4e7a53 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -52,6 +52,19 @@ typedef int (*i2c_slave_cb_t)(struct i2c_client *client, struct module; struct property_entry; +/* SMBus 3.0 extends the maximum block read/write size to 255 (from 32). + * The larger size is only supported by some drivers, indicated by + * the I2C_FUNC_SMBUS_V3_BLOCK functionality bit. + */ +#define I2C_SMBUS_V3_BLOCK_MAX 255 /* As specified in SMBus 3.0 standard */ + +/* Note compatibility definition in uapi header with 32 byte block */ +union i2c_smbus_data { + __u8 byte; + __u16 word; + __u8 block[I2C_SMBUS_V3_BLOCK_MAX + 1]; /* block[0] is used for length */ +}; + #if IS_ENABLED(CONFIG_I2C) /* Return the Frequency mode string based on the bus frequency */ const char *i2c_freq_mode_string(u32 bus_freq_hz); |