linux-kernel - Re: [RFC PATCH 1/2] i2c: Add i2c_verify_device

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Date:   Sun, 8 Apr 2018 11:08:39 +0200
From:   Peter Rosin <peda@...ntia.se>
To:     Wolfram Sang <wsa@...-dreams.de>,
        Guenter Roeck <linux@...ck-us.net>
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/2] i2c: Add i2c_verify_device_id() to verify device
 id

On 2018-04-08 09:34, Wolfram Sang wrote:
> Hi,
> 
> On Mon, Mar 19, 2018 at 09:10:58AM -0700, Guenter Roeck wrote:
>> Commit dde67eb1beeb ("i2c: add i2c_get_device_id() to get the standard
>> I2C device id") added a function to return the standard I2C device ID.
>> Use that function to verify the device ID of a given device.
> 
> I am very open to these patches, just...
> 
>>
>> Cc: Peter Rosin <peda@...ntia.se>
>> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>> ---
>> RFC:
>> - Compile tested only
> 
> ... I would really like to have them tested. After that happened, Peter
> and I can figure out who should apply them for seamless upstreaming.
> 
>> - Should there also be I2C_DEVICE_PART_ID_ANY to enable maching
>>   against all parts from a given manufacturer ?
> 
> Can't we just add it when we need it?
> 
>> +		dev_err(&client->dev, "unexpected device id %03x-%03x-%x\n",
>> +			real_id.manufacturer_id, real_id.part_id,
>> +			real_id.die_revision);
>> +		return -ENODEV;
> 
> I wonder about the ERR loglevel. ENODEV is not an error, I'd think?

Well, in this case someone has said that I2C addr <xyz> is a <uvw> device,
but when verifying the actual device at that addr, that's not what is
found. Hence, I think an error is appropriate? On the other hand, a driver
that can handle different kinds of devices might not want the error. But
for that case, maybe the driver should be using i2c_get_device_id() and
figure out the details by itself?

Cheers,
Peter