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Date: Fri, 29 Jul 2011 13:43:46 +0100
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: viresh kumar <viresh.kumar@st.com>
Cc: "linus.walleij@linaro.org" <linus.walleij@linaro.org>,
        Pratyush ANAND <pratyush.anand@st.com>,
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Subject: Re: [PATCH 00/18] dmaengine/amba-pl08x updates
Message-ID: <20110729124346.GL25640@n2100.arm.linux.org.uk>
References: <cover.1311936523.git.viresh.kumar@st.com> <20110729105759.GE25640@n2100.arm.linux.org.uk> <4E329616.2030505@st.com> <20110729111920.GK25640@n2100.arm.linux.org.uk> <4E329848.7070606@st.com>
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On Fri, Jul 29, 2011 at 04:53:52PM +0530, viresh kumar wrote:
> On 07/29/2011 04:49 PM, Russell King - ARM Linux wrote:
> > Ok, so lets have the driver explicitly enforce one SG entry if peripheral
> > flow is set.  It would also be a good idea to pass not zero length, but
> > the real transfer size in the SG entry for the sake of having the API
> > know the full information about the transfer.
> 
> In my case, JPEG driver doesn't know how much data to transfer. So i have to
> send zero from there. Also, i am not sure why would peripheral needs to be
> flow controller if the peripherals driver already know how much to transfer?

If the jpeg driver doesn't know how much data will be transferred, how
can it allocate a buffer for the device to DMA into?