From e780535fb34402b6a99fe753f2aaaa531dd40e21 Mon Sep 17 00:00:00 2001 From: Matt Porter Date: Wed, 6 Mar 2013 19:56:05 +0000 Subject: [PATCH] dmaengine: add dma_get_slave_sg_limits() Add a dmaengine API to retrieve slave SG transfer limits. The API is optionally implemented by dmaengine drivers and when unimplemented will return a NULL pointer. A client driver using this API provides the required dma channel, address width, and burst size of the transfer. dma_get_slave_sg_limits() returns an SG limits structure with the maximum number and size of SG segments that the given channel can handle. Signed-off-by: Matt Porter Signed-off-by: Joel A Fernandes --- include/linux/dmaengine.h | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index 0c72b89..4132aa2 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -373,6 +373,18 @@ struct dma_slave_config { unsigned int slave_id; }; +/* struct dma_slave_sg_limits - expose SG transfer limits of a channel + * + * @max_seg_nr: maximum number of SG segments supported on a SG/SLAVE + * channel (0 for no maximum or not a SG/SLAVE channel) + * @max_seg_len: maximum length of SG segments supported on a SG/SLAVE + * channel (0 for no maximum or not a SG/SLAVE channel) + */ +struct dma_slave_sg_limits { + u32 max_seg_nr; + u32 max_seg_len; +}; + static inline const char *dma_chan_name(struct dma_chan *chan) { return dev_name(&chan->dev->device); @@ -535,6 +547,7 @@ struct dma_tx_state { * struct with auxiliary transfer status information, otherwise the call * will just return a simple status code * @device_issue_pending: push pending transactions to hardware + * @device_slave_sg_limits: return the slave SG capabilities */ struct dma_device { @@ -600,6 +613,9 @@ struct dma_device { dma_cookie_t cookie, struct dma_tx_state *txstate); void (*device_issue_pending)(struct dma_chan *chan); + struct dma_slave_sg_limits *(*device_slave_sg_limits)( + struct dma_chan *chan, enum dma_slave_buswidth addr_width, + u32 maxburst); }; static inline int dmaengine_device_control(struct dma_chan *chan, @@ -961,6 +977,30 @@ dma_set_tx_state(struct dma_tx_state *st, dma_cookie_t last, dma_cookie_t used, } } +/** + * dma_get_slave_sg_limits - get DMAC SG transfer capabilities + * @chan: target DMA channel + * @addr_width: address width of the DMA transfer + * @maxburst: maximum DMA transfer burst size + * + * Get SG transfer capabilities for a specified channel. If the dmaengine + * driver does not implement SG transfer capabilities then NULL is + * returned. + */ +static inline struct dma_slave_sg_limits +*dma_get_slave_sg_limits(struct dma_chan *chan, + enum dma_slave_buswidth addr_width, + u32 maxburst) +{ + if (chan->device->device_slave_sg_limits) + return chan->device->device_slave_sg_limits(chan, + addr_width, + maxburst); + + return NULL; +} + + #ifdef CONFIG_DMA_ENGINE struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type); enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie); -- 1.8.3.1