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i2c: core: Allow 255 byte transfers for SMBus 3.x

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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>
This commit is contained in:
Matt Johnston 2021-11-15 10:49:21 +08:00 • committed by David S. Miller
parent cc0be1ad68
commit 13cae4a104
3 changed files with 30 additions and 8 deletions
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5
include/uapi/linux/i2c.h
View file

@ -108,6 +108,7 @@ struct i2c_msg {
#define I2C_FUNC_SMBUS_READ_I2C_BLOCK 0x04000000 /* I2C-like block xfer */
#define I2C_FUNC_SMBUS_WRITE_I2C_BLOCK 0x08000000 /* w/ 1-byte reg. addr. */
#define I2C_FUNC_SMBUS_HOST_NOTIFY 0x10000000 /* SMBus 2.0 or later */
#define I2C_FUNC_SMBUS_V3_BLOCK 0x20000000 /* Device supports 255 byte block */
#define I2C_FUNC_SMBUS_BYTE (I2C_FUNC_SMBUS_READ_BYTE | \
I2C_FUNC_SMBUS_WRITE_BYTE)
@ -137,13 +138,15 @@ struct i2c_msg {
/*
* Data for SMBus Messages
*/
#define I2C_SMBUS_BLOCK_MAX 32 /* As specified in SMBus standard */
#define I2C_SMBUS_BLOCK_MAX 32 /* As specified in SMBus 2.0 standard */
#ifndef __KERNEL__
union i2c_smbus_data {
__u8 byte;
__u16 word;
__u8 block[I2C_SMBUS_BLOCK_MAX + 2]; /* block[0] is used for length */
/* and one more for user-space compatibility */
};
#endif
/* i2c_smbus_xfer read or write markers */
#define I2C_SMBUS_READ 1