linux-kernel - Re: [PATCH v1 2/6] [media] ov9650: add device tree support

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Date:   Tue, 27 Jun 2017 10:14:46 +0000
From:   Hugues FRUCHET <hugues.fruchet@...com>
To:     Sakari Ailus <sakari.ailus@....fi>,
        "H. Nikolaus Schaller" <hns@...delico.com>
CC:     Sylwester Nawrocki <sylvester.nawrocki@...il.com>,
        Guennadi Liakhovetski <g.liakhovetski@....de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "Benjamin Gaignard" <benjamin.gaignard@...aro.org>,
        Yannick FERTRE <yannick.fertre@...com>
Subject: Re: [PATCH v1 2/6] [media] ov9650: add device tree support



On 06/27/2017 07:36 AM, Sakari Ailus wrote:
> On Mon, Jun 26, 2017 at 07:46:34PM +0200, H. Nikolaus Schaller wrote:
>> Hi,
>>
>>> Am 26.06.2017 um 18:31 schrieb Sakari Ailus <sakari.ailus@....fi>:
>>>
>>> Hi Hugues,
>>>
>>> On Thu, Jun 22, 2017 at 05:05:38PM +0200, Hugues Fruchet wrote:
>>>> @@ -1545,15 +1577,22 @@ static int ov965x_remove(struct i2c_client *client)
>>>> }
>>>>
>>>> static const struct i2c_device_id ov965x_id[] = {
>>>> -	{ "OV9650", 0 },
>>>> -	{ "OV9652", 0 },
>>>> +	{ "OV9650", 0x9650 },
>>>> +	{ "OV9652", 0x9652 },
>>>
>>> This change does not appear to match with the patch description nor it the
>>> information is used. How about not changing it, unless there's a reason to?
>>> The same for the data field of the of_device_id array below.
>>
>> I think it could/should be used to check if the camera chip that is found
>> by reading the product-id and version registers does match what the device
>> tree expects and abort probing on a mismatch.
> 
> Makes sense. But it should be a separate patch, shouldn't it?
> 
> You could also put the id to the ops struct, and choose the ops struct that
> way. Entirely up to you.
> 

I'll suggest to skip the id check between DT compatible string and real 
device id read from sensor, this is not something I see in other drivers 
currently.
But I would suggest to keep in a separate patch the switch of device id 
names to lower case in order to align with other omnivision cameras and 
not introduce upper/lower case potential bugs in DT later on (as the one 
encountered by Nikolaus):

  [media] ov9650: switch i2c device id to lower case

  static const struct i2c_device_id ov965x_id[] = {
-	{ "OV9650", 0 },
-	{ "OV9652", 0 },
+	{ "ov9650", 0 },
+	{ "ov9652", 0 },


  [media] ov9650: add device tree support

+static const struct of_device_id ov965x_of_match[] = {
+	{ .compatible = "ovti,ov9650", },
+	{ .compatible = "ovti,ov9652", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, ov965x_of_match);
+
  static struct i2c_driver ov965x_i2c_driver = {
  	.driver = {
  		.name	= DRIVER_NAME,
+		.of_match_table = of_match_ptr(ov965x_of_match),