Re: [PATCH v5 2/2] DMAEngine: Add DMAEngine driver based on old MSMADM DMA APIs
From: Linus Walleij
Date: Mon Mar 26 2012 - 03:17:57 EST
On Thu, Mar 22, 2012 at 3:23 PM, Ravi Kumar V <kumarrav@xxxxxxxxxxxxxx> wrote:
This stuff:
> +enum adm_flush_type {
> + ADM_FORCED_FLUSH,
> + ADM_GRACEFUL_FLUSH,
> +};
> +/*
> + * Controlling the hardware channel like stopping, flushing.
> + */
> +static int msm_dma_chan_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
> + unsigned long arg)
> +{
> + enum adm_flush_type cmd_type = arg;
> +
> + if (cmd == DMA_TERMINATE_ALL) {
> + switch (cmd_type) {
> + case ADM_GRACEFUL_FLUSH:
> + msm_dmov_stop_cmd(chan->chan_id, NULL, 1);
> + break;
> + case ADM_FORCED_FLUSH:
> + /*
> + * We treate default as forced flush
> + * so we fall through
> + */
> + default:
> + msm_dmov_stop_cmd(chan->chan_id, NULL, 0);
> + break;
> + }
> + }
> + return 0;
> +}
This is an interesting way of using the opaque arg. Can you describe
the different semantics of graceful vs forced flush so we understand
the usecases for them?
DMA_TERMINATE_ALL is usually not very graceful.
DMA_PAUSE might be the semantic you're looking for as the
graceful path, and then you can do away with this strange
enum altogether.
Yours,
Linus Walleij
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