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

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Message-ID: <20120319080402.GA15965@polaris.bitmath.org>
Date:	Mon, 19 Mar 2012 09:04:02 +0100
From:	"Henrik Rydberg" <rydberg@...omail.se>
To:	Daniel Kurtz <djkurtz@...omium.org>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Joonyoung Shim <jy0922.shim@...sung.com>,
	Iiro Valkonen <iiro.valkonen@...el.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Benson Leung <bleung@...omium.org>,
	Yufeng Shen <miletus@...omium.org>
Subject: Re: [PATCH 06/20] Input: atmel_mxt_ts - allow writing to object
 sysfs entry

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@...omium.org>
> ---

Perhaps you could give an example of why this is needed?

Thanks,
Henrik
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