[PATCH] dmaengine: delete redundant chan_id and chancnt initialization in dma drivers
21cnbao at gmail.com
Wed Sep 21 20:08:44 EDT 2011
2011/9/21 Jassi Brar <jassisinghbrar at gmail.com>:
> On Fri, Sep 16, 2011 at 3:13 PM, Barry Song <Baohua.Song at csr.com> wrote:
>> dma_async_device_register will re-init chan_id and chancnt,
>> so whatever chan_id and chancnt are set in drivers, they will
>> be re-written by dma_async_device_register.
>> Cc: Nicolas Ferre <nicolas.ferre at atmel.com>
>> Cc: Viresh Kumar <viresh.kumar at st.com>
>> Cc: Vinod Koul <vinod.koul at intel.com>
>> Cc: Piotr Ziecik <kosmo at semihalf.com>
>> Cc: Yong Wang <yong.y.wang at intel.com>
>> Cc: Jaswinder Singh <jassi.brar at samsung.com>
>> Cc: Pelagicore AB <info at pelagicore.com>
>> Signed-off-by: Barry Song <Baohua.Song at csr.com>
>> drivers/dma/at_hdmac.c | 5 ++---
>> drivers/dma/dw_dmac.c | 5 ++---
>> drivers/dma/intel_mid_dma.c | 2 --
>> drivers/dma/mpc512x_dma.c | 1 -
>> drivers/dma/pch_dma.c | 2 --
>> drivers/dma/pl330.c | 2 --
>> drivers/dma/timb_dma.c | 3 +--
> Apparently ....
> still write to chan_id.
> still write to chancnt
> Most of them are simply a matter of removal, but some seem
> like really depending upon setting them(?)
> Anyways, even after you modify those as well, chan_id and chancnt
> are rendered overstaying guests in dmaengine core. Because chan_id
> of each channel would be _precisely_ the order in which the
> _dmac-driver_ added the channel to the 'channels' list.
> So if their values are _always_ gonna be just contiguously incrementing
> why need variables for that in the dmaengine api?
> Dmac drivers could use local variables for that.
> OTOH, why not chan_id be left solely for use by dmac drivers read by the
> dmaengine only to create sysfs entries ?
actually i don't like the way dmaengine core handles chan_id. in my
opinion, every dmac only needs to tell dmaengine core the chan_base.
then dmaengine core set the id in a global scale.
for example, if you have two dmac in system:
dmac0 chan_base 0
dmac1 chan_base 16
then core will have chan 0~31 by chan_id from 0 to 31 but not
client drivers can request a specific chan_id just like it can request a gpio.
now dmac drivers and dmaengine core have repeated chan_id and chancnt,
anyway, it is a problem that should be fixed at first. then i'd like
to have some common function to support the request of specific
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
More information about the linux-arm-kernel