On Wed, Mar 25, 2015 at 04:33:20PM +0200, Irina Tirdea wrote: > There are devices that need to handle block transactions > regardless of the capabilities exported by the adapter. > For performance reasons, they need to use i2c read blocks > if available, otherwise emulate the block transaction with word > or byte transactions. > > Add support for a helper function that would read a data block > using the best transfer available: I2C_FUNC_SMBUS_READ_I2C_BLOCK, > I2C_FUNC_SMBUS_READ_WORD_DATA or I2C_FUNC_SMBUS_READ_BYTE_DATA. > > Signed-off-by: Irina Tirdea <[email protected]> > --- > > Hi, > > This is a new API proposal to handle i2c block emulation in the > core instead of the driver code. > > This is needed for a set of iio sensor changes ([1], [2], [3]) > that would otherwise duplicate this code. There are also some > usages of this functionality in the kernel (e.g. eeprom driver at24). > > Please let me know what you think.
I am open to add something like this. One change I'd like to request is to introduce a user, e.g. convert at24. > > Thanks, > Irina > > [1] https://lkml.org/lkml/2015/2/16/408 > [2] https://lkml.org/lkml/2015/2/16/413 > [3] https://lkml.org/lkml/2015/2/16/402 > > drivers/i2c/i2c-core.c | 62 > ++++++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/i2c.h | 3 +++ > 2 files changed, 65 insertions(+) > > diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c > index fe80f85..2579f7d 100644 > --- a/drivers/i2c/i2c-core.c > +++ b/drivers/i2c/i2c-core.c > @@ -2907,6 +2907,68 @@ trace: > } > EXPORT_SYMBOL(i2c_smbus_xfer); > > +/** > + * i2c_smbus_read_i2c_block_data_or_emulated - read block or emulate > + * @client: Handle to slave device > + * @command: Byte interpreted by slave > + * @length: Size of data block; SMBus allows at most 32 bytes > + * @values: Byte array into which data will be read; big enough to hold > + * the data returned by the slave. SMBus allows at most 32 bytes. Sidenote: SMBus3 allows 255 byte, but we don't support that (yet), so this is okay for now. > + * > + * This executes the SMBus "block read" protocol if supported by the adapter. > + * If block read is not supported, it emulates it using either word or byte > + * read protocols depending on availability. Here I'd like to see a warning that people should double-check if their I2C slave does support that. Sometimes one can't exchange a block transfer with a byte transfer. > + */ > +s32 i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client > *client, > + u8 command, u8 length, u8 *values) > +{ > + u8 i; > + int status; > + > + if (length > I2C_SMBUS_BLOCK_MAX) > + length = I2C_SMBUS_BLOCK_MAX; > + > + if (i2c_check_functionality(client->adapter, > + I2C_FUNC_SMBUS_READ_I2C_BLOCK)) { > + return i2c_smbus_read_i2c_block_data(client, command, > + length, values); > + } else if (i2c_check_functionality(client->adapter, > + I2C_FUNC_SMBUS_READ_WORD_DATA | > + I2C_FUNC_SMBUS_READ_BYTE_DATA)) { What about skipping the need for READ_BYTE_DATA and dump the byte which was maybe read too much? > + for (i = 0; (i + 2) <= length; i += 2) { > + status = i2c_smbus_read_word_data(client, command + i); > + if (status < 0) > + return status; > + values[i] = status & 0xff; > + values[i+1] = status >> 8; > + } > + if (i < length) { > + status = i2c_smbus_read_byte_data(client, command + i); > + if (status < 0) > + return status; > + values[i] = status; > + i++; > + } > + return i; > + } else if (i2c_check_functionality(client->adapter, > + I2C_FUNC_SMBUS_READ_BYTE_DATA)) { > + for (i = 0; i < length; i++) { > + status = i2c_smbus_read_byte_data(client, command + i); > + if (status < 0) > + return status; > + values[i] = status; > + } > + return i; > + } > + > + dev_err(&client->adapter->dev, "Unsupported transactions: %d,%d,%d\n", > + I2C_SMBUS_I2C_BLOCK_DATA, I2C_SMBUS_WORD_DATA, > + I2C_SMBUS_BYTE_DATA); > + > + return -EOPNOTSUPP; > +} > +EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data_or_emulated); Thanks, Wolfram
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