Re: [PATCH 06/20] Input: atmel_mxt_ts - allow writing to object sysfs entry

Daniel Kurtz wrote:

Userspace can write a 24-bit value (encoded as a 6 character hex string)
to the 'object' sysfs entry to modify a single byte of the object table.
The hex string encodes a 3 bytes, in the following format:
 TTFFVV

Where:
 TT = object type
 FF = object offset
 VV = byte value

The object table is modified in device ram, which means the change is
volatile, and will be overwritten on the next device reset.  To make
changes permanent, the new settings should be persisted in the device's
Non-Voltatile Memory using the updatenv sysfs entry.

Also, since the device driver initializes itself by reading some values
from the object table, the entire driver may need to be unloaded and
reloaded after writing the values for the driver to stay in sync.  Whether
this is required depends on exactly which values were updated.

Signed-off-by: Daniel Kurtz <redacted>

NAK. I have several concerns about this:

1) The object sysfs entry doesn't follow the sysfs guidelines, this is
abusing it further.
2) Object type can be larger than 1 byte in the future.
3) Your interface restricts you to doing 1 byte writes. What about larger
block sizes?

In short, I think exposing the entire register space as a binary attribute
(the same way that regmap does) is a preferable solution to this
requirement, and we already have user space tools which use it.

cheers

-- 
Nick Dyer
Software Engineer, ITDev Ltd
Hardware and Software Development Consultancy
Website: http://www.itdev.co.uk