linux-kernel - Re: [PATCH 0/2] staging: comedi: per-file read/write subdevice choice

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Date:	Wed, 05 Nov 2014 09:48:49 +0000
From:	Ian Abbott <abbotti@....co.uk>
To:	Hartley Sweeten <HartleyS@...ionengravers.com>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/2] staging: comedi: per-file read/write subdevice choice

On 04/11/2014 18:44, Hartley Sweeten wrote:
> On Tuesday, November 04, 2014 11:09 AM, Ian Abbott wrote:
>> This series of patches adds a couple of ioctl codes to the Comedi core
>> to allow the current "read" and "write" subdevice to be changed after
>> opening the comedi device.  The current read and write subdevice
>> information is stored in file private data allocated for the lifetime of
>> the file object, so the notion of current "read" and "write" subdevice
>> is local to the file object and does not alter anything in the main
>> control structure for the comedi device.  An extra level of indirection
>> is now required to access the main control structure.
>>
>> I've tested the multiple "read" subdevice case using a modified version
>> of the "comedi_test" module (modifying it to clone the existing AI
>> subdevice), and a modified version of the "comedi_test" application
>> (part of the "comedilib" installation) modified to use the new ioctls.
>> There isn't any support in comedilib itself yet.
>>
>> 1) staging: comedi: prepare support for per-file read and write
>>     subdevices
>> 2) staging: comedi: add ioctls to set per-file read and write subdevice
>>
>>   drivers/staging/comedi/comedi.h          |   2 +
>>   drivers/staging/comedi/comedi_compat32.c |   2 +
>>   drivers/staging/comedi/comedi_fops.c     | 217 +++++++++++++++++++++++++++----
>>   3 files changed, 196 insertions(+), 25 deletions(-)
>
> Ian,
>
> If I understand this correctly, the user can now open the "comediX"
> device which will give then access to the default dev->read_subdev
> and dev->write_subdev. They can then use the new ioctls to change
> the read/write subdevice and use them without having the open the
> "comediX_subdY" devices.
>
> If this is correct it seems like a good idea.

That's correct.

> Reviewed-by: H Hartley Sweeten <hsweeten@...ionengravers.com>

Thanks for the review!

> Also, does this mean we can get rid of comedi_alloc_subdevice_minor()
> and the "comediX_sudbY" stuff?

That would be a bit premature at this stage.  Maybe in a year or two.

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@....co.uk> )=-
-=(                          Web: http://www.mev.co.uk/  )=-
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