lkml.org 
[lkml]   [2012]   [Mar]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 06/20] Input: atmel_mxt_ts - allow writing to object sysfs entry
On Mon, Mar 19, 2012 at 4:04 PM, Henrik Rydberg <rydberg@euromail.se> wrote:
>
> Hi Daniel,
>
> > 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 <djkurtz@chromium.org>
> > ---
>
> Perhaps you could give an example of why this is needed?
>
> Thanks,
> Henrik

The idea is to allow a a device to be calibrated via userspace. The
atmel devices have many registers for tuning properties of their
firmware.
This would be used, for example, to program an initial calibration on
a factory floor, or, to tune a device at runtime. Currently, the only
way devices are configured and calibrated is for a system integrator
to embed the entire calibration in the kernel via a binary blob in
platform_data.

Thanks,
-Daniel
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2012-03-19 09:29    [W:0.916 / U:0.228 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site