linux-kernel - Re: [RFC 2/2] dma-buf: Documentation for buffer sharing framework

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Date:	Thu, 13 Oct 2011 10:18:10 +0530
From:	"Semwal, Sumit" <sumit.semwal@...com>
To:	Randy Dunlap <rdunlap@...otime.net>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mm@...ck.org, linaro-mm-sig@...ts.linaro.org,
	dri-devel@...ts.freedesktop.org, linux-media@...r.kernel.org,
	linux@....linux.org.uk, arnd@...db.de, jesse.barker@...aro.org,
	m.szyprowski@...sung.com, rob@...com, daniel@...ll.ch,
	t.stanislaws@...sung.com, Sumit Semwal <sumit.semwal@...aro.org>
Subject: Re: [RFC 2/2] dma-buf: Documentation for buffer sharing framework

Hi Randy,
On Thu, Oct 13, 2011 at 4:00 AM, Randy Dunlap <rdunlap@...otime.net> wrote:
> On 10/11/2011 02:23 AM, Sumit Semwal wrote:
>> Add documentation for dma buffer sharing framework, explaining the
>> various operations, members and API of the dma buffer sharing
>> framework.
>>
>> Signed-off-by: Sumit Semwal <sumit.semwal@...aro.org>
>> Signed-off-by: Sumit Semwal <sumit.semwal@...com>
>> ---
>>  Documentation/dma-buf-sharing.txt |  210 +++++++++++++++++++++++++++++++++++++
<snip>
>> +    if the new buffer-user has stricter 'backing-storage constraints', and the
>> +    exporter can handle these constraints, the exporter can just stall on the
>> +    get_scatterlist till all outstanding access is completed (as signalled by
>
>                       until
>
Thanks for your review; I will update all these in the next version.
>> +    put_scatterlist).
>> +    Once all ongoing access is completed, the exporter could potentially move
>> +    the buffer to the stricter backing-storage, and then allow further
>> +    {get,put}_scatterlist operations from any buffer-user from the migrated
>> +    backing-storage.
>> +
>> +   If the exporter cannot fulfill the backing-storage constraints of the new
>> +   buffer-user device as requested, dma_buf_attach() would return an error to
>> +   denote non-compatibility of the new buffer-sharing request with the current
>> +   buffer.
>> +
>> +   If the exporter chooses not to allow an attach() operation once a
>> +   get_scatterlist has been called, it simply returns an error.
>> +
>> +- mmap file operation
>> +   An mmap() file operation is provided for the fd associated with the buffer.
>> +   If the exporter defines an mmap operation, the mmap() fop calls this to allow
>> +   mmap for devices that might need it; if not, it returns an error.
>> +
>> +References:
>> +[1] struct dma_buf_ops in include/linux/dma-buf.h
>> +[2] All interfaces mentioned above defined in include/linux/dma-buf.h
>
>
> --
> ~Randy
> *** Remember to use Documentation/SubmitChecklist when testing your code ***
>
Best regards,
~Sumit.
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