lkml.org 
[lkml]   [2011]   [Oct]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    SubjectRe: [PATCHv4] DMAEngine: Define interleaved transfer request api
    From
    On 14 October 2011 23:20, Bounine, Alexandre <Alexandre.Bounine@idt.com> wrote:
    >> On Fri, Oct 7, 2011 at 4:27 AM, Jassi Brar
    > <jaswinder.singh@linaro.org>
    >> wrote:
    >> > On 7 October 2011 11:15, Vinod Koul <vinod.koul@intel.com> wrote:
    >> >
    >> >> Thru this patch Jassi gave a very good try at merging DMA_SLAVE and
    >> >> memcpy, but more we debate this, I am still not convinced about
    >> merging
    >> >> memcpy and DMA_SLAVE yet.
    >> >>
    >> > Nobody is merging memcpy and DMA_SLAVE right away.
    >> > The api's primary purpose is to support interleave transfers.
    >> > Possibility to merge other prepares into this is a side-effect.
    >> >
    >> >> I would still argue that if we split this on same lines as current
    >> >> mechanism, we have clean way to convey all details for both cases.
    >> >>
    >> > Do you mean to have separate interleaved transfer apis for Slave
    >> > and Mem->Mem ? Please clarify.
    >> >
    >>
    >> This is a tangent, but it would be nice if this API extension also
    >> covered the needs of the incoming RapidIO case which wants to specify
    >> new device context information per operation (and not once at
    >> configuration time, like slave case).  Would it be enough if the
    >> transfer template included a (struct device *context) member at the
    >> end?  Most dma users could ignore it, but RapidIO could use it to do
    >> something like:
    >>
    >>    struct rio_dev *rdev = container_of(context, typeof(*rdev),
    > device);
    >>
    >> That might not be enough, but I'm concerned that making the context a
    >> (void *) is too flexible.  I'd rather have something like this than
    >> acquiring a lock in rio_dma_prep_slave_sg() and holding it over
    >> ->prep().  The alternative is to extend device_prep_slave_sg to take
    >> an extra parameter, but that impacts all other slave implementations
    >> with a dead parameter.
    >>
    >
    > Having context limited to the device structure will not be enough for
    > RapidIO because of 66-bit target address (dma_addr_t will not work
    > here).
    > Probably that range is out of practical use at this moment but it is
    > defined by RIO specification and I would prefer to deal with it now
    > instead of postponing it for future. Passing context using (void *) will
    > solve this.
    >
    OK so you need a void* to contain all info. Agreed.
    But doesn't the info, pointed to by this (void *), remain same for every
    transfer to a particular target/remote device ?
    If so, couldn't you stick this (void *) to the virtual channel's
    'private' ? 'private' :D
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2011-10-14 20:39    [W:3.033 / U:0.320 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site