On 10/15/2013 10:22 AM, Nicolin Chen wrote:
Hi Lars,
On Tue, Oct 15, 2013 at 10:08:52AM +0200, Lars-Peter Clausen wrote:
On 10/15/2013 09:49 AM, Nicolin Chen wrote:
Each implementation of gerneric pcm dmaengine has been naturally limited by the pre-defined gerneric functions. Thus add an extra interface for user to create a backdoor so that they can override those fixed functions for some uncommon requirements: using on-chip memory for DMA buffers and accordingly different mmap function for example, while at the meantime, they can continue to benifit from the concise and wise generic pcm dmaengine.
Signed-off-by: Nicolin Chen b42378@freescale.com
We do have the dmaengine pcm helper functions (sound/core/pcm_dmaengine.c) and the generic dmaengine pcm ASoC driver (sound/soc/soc-generic-dmaengine-pcm.c). The generic dmaengine pcm ASoC driver uses the dmaengine pcm helper functions, but it is not the only user of them. So your patch breaks all other users of the helper functions.
The helper functions are designed in a way that you can either wrap them in your own pcm driver driver or not use them at all. E.g. take a look at sound/soc/omap/omap-pcm.c on how to overwrite specific functions.
- Lars
If this modification to sound/core/pcm_dmaengine.c is not fair, what about moving the modification to soc-gerneric-dmaengine-pcm.c?
For example, instead of using snd_dmaengine_pcm_trigger() directly in gerneric soc dmaengine driver, we create a new one inside gerneric soc dmaengine driver and check the override:
static int snd_soc_dmaengine_pcm_trigger(substream, cmd) { if (config->driver->ops->trigger) return config->driver->ops->trigger(substream, cmd); return snd_dmaengine_pcm_trigger(substream, cmd); }
Since it happens inside generic dmaengine pcm ASoC driver, it won't break those helper functions.
I'm trying this just because I hope generic dmaengine can be more flexible Admittedly, using helper functions might be more plausible way in current ASoC structure. However, there might be so much change for an generic soc dmaengine implementation even if it just wants to override one single func.
Well the idea of the generic dmaengine driver is to be generic and not require SoC specific hacks since those should not be necessary if things are done right. What exactly do you want to implement in the overwritten ops?
- Lars