Subject: Re: Support on vendor id and device id
To: Harsha Rao <harshrao464@gmail.com>,
        Arend van Spriel <arend.vanspriel@broadcom.com>
Cc: linux-wireless@vger.kernel.org
References: <CAPcv9S3wyPd5jD1PZWtDf-mRicmzRmz00qh5Jbov_N_egBAEZg@mail.gmail.com>
 <5A953DBE.9070805@broadcom.com>
 <CAPcv9S1fZfrg3AV3GoWG-CaTkonpQyiHY6twvhS_ikXnj00t4g@mail.gmail.com>
From: Larry Finger <Larry.Finger@lwfinger.net>
Message-ID: <68f5549d-b8ad-85fb-4e80-50c53cac8108@lwfinger.net> (sfid-20180227_161457_682878_BC863ADD)
Date: Tue, 27 Feb 2018 09:14:52 -0600
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Sender: linux-wireless-owner@vger.kernel.org

On 02/27/2018 07:30 AM, Harsha Rao wrote:
> On Tue, Feb 27, 2018 at 4:45 PM, Arend van Spriel
> <arend.vanspriel@broadcom.com> wrote:
>> On 2/27/2018 11:16 AM, Harsha Rao wrote:
>>>
>>> Hi folks,
>>> I am developing a new wifi driver for our sdio based wifi device.
>>>
>>> I see that SDIO_VENDOR_ID and SDIO_DEVICE_ID for our device (We had
>>> bought the SDIO IP from 3rd party)  is already  been used by some
>>> other vendor and its already into staging .
>>>
>>> Please suggest me how can I move forward to submit the driver for staging.
>>
>>
>> Can you be more specific about the conflicting vendor id and device id?
> 
> Hi,
> My driver kicks in  with vendor id 0x296 and device id 0x5347.
> But when I grepped the the kernel source I could see an other driver
> wilc1000 using the same vendor ID and device ID
> ( We have a different hw than them !)
> 
>>> Is there a way to reconfigure the values in the SDIO host for
>>> different value or does Linux allow two drivers with same values to
>>> survive mutual exclusively
>>
>>
>> First come first serve. When a device is detected, the driver core looks for
>> drivers supporting it based on device table and the first that successfully
>> returns from the .probe() callback is bound to the device.
>>
>> Regards,
>> Arend
> 
> Does Linux allow two drivers with conflicting device and vendor IDs to
> stay on in kernel ?

Yes. We have a similar situation with the rtl8192e driver in staging and the 
rtl8192se driver in the wireless tree, which share PCI ID 0bda:8192. Our 
solution was to insert code in the probe routine that tests some value in 
addition to the PCI ID. In our case, that was the PCI revision id. Line 2496 of 
file drivers/staging/rtl8192e/rtl8192e/rtl_core.c shows the test in the staging 
driver.

The downsides of this unfortunate duplication are that if the wrong driver loads 
first, then it remains loaded, you will need to cooperate with the maintainer of 
the other driver to insert the extra detection code, and you may need to do 
quite a bit of processing to be able to determine whether you have the correct 
device.

Larry