Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 4b2643d7 authored by Jean Delvare's avatar Jean Delvare Committed by Jean Delvare
Browse files

i2c: Fix the i2c_smbus_read_i2c_block_data() prototype 



Let the drivers specify how many bytes they want to read with
i2c_smbus_read_i2c_block_data(). So far, the block count was
hard-coded to I2C_SMBUS_BLOCK_MAX (32), which did not make much sense.
Many driver authors complained about this before, and I believe it's
about time to fix it. Right now, authors have to do technically stupid
things, such as individual byte reads or full-fledged I2C messaging,
to work around the problem. We do not want to encourage that.

I even found that some bus drivers (e.g. i2c-amd8111) already
implemented I2C block read the "right" way, that is, they didn't
follow the old, broken standard. The fact that it was never noticed
before just shows how little i2c_smbus_read_i2c_block_data() was used,
which isn't that surprising given how broken its prototype was so far.

There are some obvious compatiblity considerations:
* This changes the i2c_smbus_read_i2c_block_data() prototype. Users
  outside the kernel tree will notice at compilation time, and will
  have to update their code.
* User-space has access to i2c_smbus_xfer() directly using i2c-dev, so
  the changed expectations would affect tools such as i2cdump. In order
  to preserve binary compatibility, we give I2C_SMBUS_I2C_BLOCK_DATA
  a new numeric value, and define I2C_SMBUS_I2C_BLOCK_BROKEN with the
  old numeric value. When i2c-dev receives a transaction with the
  old value, it can convert it to the new format on the fly.

Signed-off-by: default avatarJean Delvare <khali@linux-fr.org>
parent ba7fbb72

Documentation/i2c/chips/max6875

+1 −1
Original line number Diff line number Diff line
@@ -99,7 +99,7 @@ And then read the data 


  or



  count = i2c_smbus_read_i2c_block_data(fd, 0x84, buffer);

  count = i2c_smbus_read_i2c_block_data(fd, 0x84, 16, buffer);



The block read should read 16 bytes.

0x84 is the block read command.

Documentation/i2c/writing-clients

+1 −1
Original line number Diff line number Diff line
@@ -571,7 +571,7 @@ SMBus communication 
                                        u8 command, u8 length,

                                        u8 *values);

  extern s32 i2c_smbus_read_i2c_block_data(struct i2c_client * client,

                                           u8 command, u8 *values);

                                           u8 command, u8 length, u8 *values);



These ones were removed in Linux 2.6.10 because they had no users, but could

be added back later if needed:

drivers/i2c/busses/i2c-powermac.c

+1 −2
Original line number Diff line number Diff line
@@ -121,8 +121,7 @@ static s32 i2c_powermac_smbus_xfer( struct i2c_adapter* adap, 
		if (rc)

			goto bail;

		rc = pmac_i2c_xfer(bus, addrdir, 1, command,

				   read ? data->block : &data->block[1],

				   data->block[0]);

				   &data->block[1], data->block[0]);

		break;



        default:

drivers/i2c/busses/i2c-viapro.c

+1 −1
Original line number Diff line number Diff line
@@ -235,7 +235,7 @@ static s32 vt596_access(struct i2c_adapter *adap, u16 addr, 
		if (!(vt596_features & FEATURE_I2CBLOCK))

			goto exit_unsupported;

		if (read_write == I2C_SMBUS_READ)

			outb_p(I2C_SMBUS_BLOCK_MAX, SMBHSTDAT0);

			outb_p(data->block[0], SMBHSTDAT0);

		/* Fall through */

	case I2C_SMBUS_BLOCK_DATA:

		outb_p(command, SMBHSTCMD);

drivers/i2c/busses/scx200_acb.c

+0 −2
Original line number Diff line number Diff line
@@ -310,8 +310,6 @@ static s32 scx200_acb_smbus_xfer(struct i2c_adapter *adapter, 
		break;



	case I2C_SMBUS_I2C_BLOCK_DATA:

		if (rw == I2C_SMBUS_READ)

			data->block[0] = I2C_SMBUS_BLOCK_MAX; /* For now */

		len = data->block[0];

		if (len == 0 || len > I2C_SMBUS_BLOCK_MAX)

			return -EINVAL;