Re: [uclinux-dist-devel] touch screen ads7846/7843 devicetree support

[Thomas Chou <thomas-SDxUXYEhEBiCuPEqFHbRBg@public.gmane.org>]

On 02/03/2011 12:03 AM, Grant Likely wrote:
> On Thu, Jan 27, 2011 at 12:24:01PM +0000, Hennerich, Michael wrote:
>> Thomas Chou wrote on 2011-01-27:
>>> On 01/27/2011 02:18 PM, Mike Frysinger wrote:
>>>> On Thu, Jan 27, 2011 at 01:10, Thomas Chou wrote:
>>>>> We need devicetree support on ads7846/7843 touch screen driver. Do
>>>>> you have plan on it? We are moving to devicetree on nios2, so do
>>> arm/mips/x86.
>>>>
>>>> what part are you using exactly ?
>>>> -mike
>>>>
>>>
>>> ad7843 is used in a popular nios2 dev kit, NEEK.
>>
>> This driver is a SPI bus client driver. PPC is using devicetree for ages now,
>> and they don't have problems instantiating this or any other SPI bus driver.
>
> However, the method used is by applying a heuristic (of_modalias_node)
> which tries to name the device in a way that will match an existing
> device driver.  It works for a lot of spi drivers, but it isn't
> always reliable.
>
> Alternatively, if of_match_table is populated in the spi_driver, then
> the normal device tree match behaviour will always work.

Thanks. The driver did match with the heuristic. But it needs to 
determine pen state. I will try to bind a gpio node in dts.

linux/spi/ads7846.h

int	gpio_pendown;		/* the GPIO used to decide the pendown
				 * state if get_pendown_state == NULL
				 */

- Thomas