Date:	Sun, 28 Sep 2014 21:27:54 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:	Dan Williams <dan.j.williams@...el.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	dmaengine@...r.kernel.org, Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Antoine Ténart <antoine@...e-electrons.com>,
	Thomas Petazzoni <thomas@...e-electrons.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Boris Brezillon <boris@...e-electrons.com>,
	Matt Porter <matt.porter@...aro.org>,
	laurent.pinchart@...asonboard.com,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>
Subject: Re: [PATCH v2 1/2] Documentation: dmaengine: Move the current doc
 to a folder of its own

On Fri, Sep 26, 2014 at 05:40:34PM +0200, Maxime Ripard wrote:
> Move the current client-side documentation to a subfolder to prepare the
> introduction of a provider-side API documentation.

for these kind of move patches pls use -M option which will show the move
only


-- 
~Vinod
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
> ---
>  Documentation/dmaengine.txt        | 199 -------------------------------------
>  Documentation/dmaengine/client.txt | 199 +++++++++++++++++++++++++++++++++++++
>  2 files changed, 199 insertions(+), 199 deletions(-)
>  delete mode 100644 Documentation/dmaengine.txt
>  create mode 100644 Documentation/dmaengine/client.txt
> 
> diff --git a/Documentation/dmaengine.txt b/Documentation/dmaengine.txt
> deleted file mode 100644
> index 573e28ce9751..000000000000
> --- a/Documentation/dmaengine.txt
> +++ /dev/null
> @@ -1,199 +0,0 @@
> -			DMA Engine API Guide
> -			====================
> -
> -		 Vinod Koul <vinod dot koul at intel.com>
> -
> -NOTE: For DMA Engine usage in async_tx please see:
> -	Documentation/crypto/async-tx-api.txt
> -
> -
> -Below is a guide to device driver writers on how to use the Slave-DMA API of the
> -DMA Engine. This is applicable only for slave DMA usage only.
> -
> -The slave DMA usage consists of following steps:
> -1. Allocate a DMA slave channel
> -2. Set slave and controller specific parameters
> -3. Get a descriptor for transaction
> -4. Submit the transaction
> -5. Issue pending requests and wait for callback notification
> -
> -1. Allocate a DMA slave channel
> -
> -   Channel allocation is slightly different in the slave DMA context,
> -   client drivers typically need a channel from a particular DMA
> -   controller only and even in some cases a specific channel is desired.
> -   To request a channel dma_request_channel() API is used.
> -
> -   Interface:
> -	struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
> -			dma_filter_fn filter_fn,
> -			void *filter_param);
> -   where dma_filter_fn is defined as:
> -	typedef bool (*dma_filter_fn)(struct dma_chan *chan, void *filter_param);
> -
> -   The 'filter_fn' parameter is optional, but highly recommended for
> -   slave and cyclic channels as they typically need to obtain a specific
> -   DMA channel.
> -
> -   When the optional 'filter_fn' parameter is NULL, dma_request_channel()
> -   simply returns the first channel that satisfies the capability mask.
> -
> -   Otherwise, the 'filter_fn' routine will be called once for each free
> -   channel which has a capability in 'mask'.  'filter_fn' is expected to
> -   return 'true' when the desired DMA channel is found.
> -
> -   A channel allocated via this interface is exclusive to the caller,
> -   until dma_release_channel() is called.
> -
> -2. Set slave and controller specific parameters
> -
> -   Next step is always to pass some specific information to the DMA
> -   driver.  Most of the generic information which a slave DMA can use
> -   is in struct dma_slave_config.  This allows the clients to specify
> -   DMA direction, DMA addresses, bus widths, DMA burst lengths etc
> -   for the peripheral.
> -
> -   If some DMA controllers have more parameters to be sent then they
> -   should try to embed struct dma_slave_config in their controller
> -   specific structure. That gives flexibility to client to pass more
> -   parameters, if required.
> -
> -   Interface:
> -	int dmaengine_slave_config(struct dma_chan *chan,
> -				  struct dma_slave_config *config)
> -
> -   Please see the dma_slave_config structure definition in dmaengine.h
> -   for a detailed explanation of the struct members.  Please note
> -   that the 'direction' member will be going away as it duplicates the
> -   direction given in the prepare call.
> -
> -3. Get a descriptor for transaction
> -
> -   For slave usage the various modes of slave transfers supported by the
> -   DMA-engine are:
> -
> -   slave_sg	- DMA a list of scatter gather buffers from/to a peripheral
> -   dma_cyclic	- Perform a cyclic DMA operation from/to a peripheral till the
> -		  operation is explicitly stopped.
> -   interleaved_dma - This is common to Slave as well as M2M clients. For slave
> -		 address of devices' fifo could be already known to the driver.
> -		 Various types of operations could be expressed by setting
> -		 appropriate values to the 'dma_interleaved_template' members.
> -
> -   A non-NULL return of this transfer API represents a "descriptor" for
> -   the given transaction.
> -
> -   Interface:
> -	struct dma_async_tx_descriptor *dmaengine_prep_slave_sg(
> -		struct dma_chan *chan, struct scatterlist *sgl,
> -		unsigned int sg_len, enum dma_data_direction direction,
> -		unsigned long flags);
> -
> -	struct dma_async_tx_descriptor *dmaengine_prep_dma_cyclic(
> -		struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
> -		size_t period_len, enum dma_data_direction direction);
> -
> -	struct dma_async_tx_descriptor *dmaengine_prep_interleaved_dma(
> -		struct dma_chan *chan, struct dma_interleaved_template *xt,
> -		unsigned long flags);
> -
> -   The peripheral driver is expected to have mapped the scatterlist for
> -   the DMA operation prior to calling device_prep_slave_sg, and must
> -   keep the scatterlist mapped until the DMA operation has completed.
> -   The scatterlist must be mapped using the DMA struct device.
> -   If a mapping needs to be synchronized later, dma_sync_*_for_*() must be
> -   called using the DMA struct device, too.
> -   So, normal setup should look like this:
> -
> -	nr_sg = dma_map_sg(chan->device->dev, sgl, sg_len);
> -	if (nr_sg == 0)
> -		/* error */
> -
> -	desc = dmaengine_prep_slave_sg(chan, sgl, nr_sg, direction, flags);
> -
> -   Once a descriptor has been obtained, the callback information can be
> -   added and the descriptor must then be submitted.  Some DMA engine
> -   drivers may hold a spinlock between a successful preparation and
> -   submission so it is important that these two operations are closely
> -   paired.
> -
> -   Note:
> -	Although the async_tx API specifies that completion callback
> -	routines cannot submit any new operations, this is not the
> -	case for slave/cyclic DMA.
> -
> -	For slave DMA, the subsequent transaction may not be available
> -	for submission prior to callback function being invoked, so
> -	slave DMA callbacks are permitted to prepare and submit a new
> -	transaction.
> -
> -	For cyclic DMA, a callback function may wish to terminate the
> -	DMA via dmaengine_terminate_all().
> -
> -	Therefore, it is important that DMA engine drivers drop any
> -	locks before calling the callback function which may cause a
> -	deadlock.
> -
> -	Note that callbacks will always be invoked from the DMA
> -	engines tasklet, never from interrupt context.
> -
> -4. Submit the transaction
> -
> -   Once the descriptor has been prepared and the callback information
> -   added, it must be placed on the DMA engine drivers pending queue.
> -
> -   Interface:
> -	dma_cookie_t dmaengine_submit(struct dma_async_tx_descriptor *desc)
> -
> -   This returns a cookie can be used to check the progress of DMA engine
> -   activity via other DMA engine calls not covered in this document.
> -
> -   dmaengine_submit() will not start the DMA operation, it merely adds
> -   it to the pending queue.  For this, see step 5, dma_async_issue_pending.
> -
> -5. Issue pending DMA requests and wait for callback notification
> -
> -   The transactions in the pending queue can be activated by calling the
> -   issue_pending API. If channel is idle then the first transaction in
> -   queue is started and subsequent ones queued up.
> -
> -   On completion of each DMA operation, the next in queue is started and
> -   a tasklet triggered. The tasklet will then call the client driver
> -   completion callback routine for notification, if set.
> -
> -   Interface:
> -	void dma_async_issue_pending(struct dma_chan *chan);
> -
> -Further APIs:
> -
> -1. int dmaengine_terminate_all(struct dma_chan *chan)
> -
> -   This causes all activity for the DMA channel to be stopped, and may
> -   discard data in the DMA FIFO which hasn't been fully transferred.
> -   No callback functions will be called for any incomplete transfers.
> -
> -2. int dmaengine_pause(struct dma_chan *chan)
> -
> -   This pauses activity on the DMA channel without data loss.
> -
> -3. int dmaengine_resume(struct dma_chan *chan)
> -
> -   Resume a previously paused DMA channel.  It is invalid to resume a
> -   channel which is not currently paused.
> -
> -4. enum dma_status dma_async_is_tx_complete(struct dma_chan *chan,
> -        dma_cookie_t cookie, dma_cookie_t *last, dma_cookie_t *used)
> -
> -   This can be used to check the status of the channel.  Please see
> -   the documentation in include/linux/dmaengine.h for a more complete
> -   description of this API.
> -
> -   This can be used in conjunction with dma_async_is_complete() and
> -   the cookie returned from dmaengine_submit() to check for
> -   completion of a specific DMA transaction.
> -
> -   Note:
> -	Not all DMA engine drivers can return reliable information for
> -	a running DMA channel.  It is recommended that DMA engine users
> -	pause or stop (via dmaengine_terminate_all) the channel before
> -	using this API.
> diff --git a/Documentation/dmaengine/client.txt b/Documentation/dmaengine/client.txt
> new file mode 100644
> index 000000000000..573e28ce9751
> --- /dev/null
> +++ b/Documentation/dmaengine/client.txt
> @@ -0,0 +1,199 @@
> +			DMA Engine API Guide
> +			====================
> +
> +		 Vinod Koul <vinod dot koul at intel.com>
> +
> +NOTE: For DMA Engine usage in async_tx please see:
> +	Documentation/crypto/async-tx-api.txt
> +
> +
> +Below is a guide to device driver writers on how to use the Slave-DMA API of the
> +DMA Engine. This is applicable only for slave DMA usage only.
> +
> +The slave DMA usage consists of following steps:
> +1. Allocate a DMA slave channel
> +2. Set slave and controller specific parameters
> +3. Get a descriptor for transaction
> +4. Submit the transaction
> +5. Issue pending requests and wait for callback notification
> +
> +1. Allocate a DMA slave channel
> +
> +   Channel allocation is slightly different in the slave DMA context,
> +   client drivers typically need a channel from a particular DMA
> +   controller only and even in some cases a specific channel is desired.
> +   To request a channel dma_request_channel() API is used.
> +
> +   Interface:
> +	struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
> +			dma_filter_fn filter_fn,
> +			void *filter_param);
> +   where dma_filter_fn is defined as:
> +	typedef bool (*dma_filter_fn)(struct dma_chan *chan, void *filter_param);
> +
> +   The 'filter_fn' parameter is optional, but highly recommended for
> +   slave and cyclic channels as they typically need to obtain a specific
> +   DMA channel.
> +
> +   When the optional 'filter_fn' parameter is NULL, dma_request_channel()
> +   simply returns the first channel that satisfies the capability mask.
> +
> +   Otherwise, the 'filter_fn' routine will be called once for each free
> +   channel which has a capability in 'mask'.  'filter_fn' is expected to
> +   return 'true' when the desired DMA channel is found.
> +
> +   A channel allocated via this interface is exclusive to the caller,
> +   until dma_release_channel() is called.
> +
> +2. Set slave and controller specific parameters
> +
> +   Next step is always to pass some specific information to the DMA
> +   driver.  Most of the generic information which a slave DMA can use
> +   is in struct dma_slave_config.  This allows the clients to specify
> +   DMA direction, DMA addresses, bus widths, DMA burst lengths etc
> +   for the peripheral.
> +
> +   If some DMA controllers have more parameters to be sent then they
> +   should try to embed struct dma_slave_config in their controller
> +   specific structure. That gives flexibility to client to pass more
> +   parameters, if required.
> +
> +   Interface:
> +	int dmaengine_slave_config(struct dma_chan *chan,
> +				  struct dma_slave_config *config)
> +
> +   Please see the dma_slave_config structure definition in dmaengine.h
> +   for a detailed explanation of the struct members.  Please note
> +   that the 'direction' member will be going away as it duplicates the
> +   direction given in the prepare call.
> +
> +3. Get a descriptor for transaction
> +
> +   For slave usage the various modes of slave transfers supported by the
> +   DMA-engine are:
> +
> +   slave_sg	- DMA a list of scatter gather buffers from/to a peripheral
> +   dma_cyclic	- Perform a cyclic DMA operation from/to a peripheral till the
> +		  operation is explicitly stopped.
> +   interleaved_dma - This is common to Slave as well as M2M clients. For slave
> +		 address of devices' fifo could be already known to the driver.
> +		 Various types of operations could be expressed by setting
> +		 appropriate values to the 'dma_interleaved_template' members.
> +
> +   A non-NULL return of this transfer API represents a "descriptor" for
> +   the given transaction.
> +
> +   Interface:
> +	struct dma_async_tx_descriptor *dmaengine_prep_slave_sg(
> +		struct dma_chan *chan, struct scatterlist *sgl,
> +		unsigned int sg_len, enum dma_data_direction direction,
> +		unsigned long flags);
> +
> +	struct dma_async_tx_descriptor *dmaengine_prep_dma_cyclic(
> +		struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
> +		size_t period_len, enum dma_data_direction direction);
> +
> +	struct dma_async_tx_descriptor *dmaengine_prep_interleaved_dma(
> +		struct dma_chan *chan, struct dma_interleaved_template *xt,
> +		unsigned long flags);
> +
> +   The peripheral driver is expected to have mapped the scatterlist for
> +   the DMA operation prior to calling device_prep_slave_sg, and must
> +   keep the scatterlist mapped until the DMA operation has completed.
> +   The scatterlist must be mapped using the DMA struct device.
> +   If a mapping needs to be synchronized later, dma_sync_*_for_*() must be
> +   called using the DMA struct device, too.
> +   So, normal setup should look like this:
> +
> +	nr_sg = dma_map_sg(chan->device->dev, sgl, sg_len);
> +	if (nr_sg == 0)
> +		/* error */
> +
> +	desc = dmaengine_prep_slave_sg(chan, sgl, nr_sg, direction, flags);
> +
> +   Once a descriptor has been obtained, the callback information can be
> +   added and the descriptor must then be submitted.  Some DMA engine
> +   drivers may hold a spinlock between a successful preparation and
> +   submission so it is important that these two operations are closely
> +   paired.
> +
> +   Note:
> +	Although the async_tx API specifies that completion callback
> +	routines cannot submit any new operations, this is not the
> +	case for slave/cyclic DMA.
> +
> +	For slave DMA, the subsequent transaction may not be available
> +	for submission prior to callback function being invoked, so
> +	slave DMA callbacks are permitted to prepare and submit a new
> +	transaction.
> +
> +	For cyclic DMA, a callback function may wish to terminate the
> +	DMA via dmaengine_terminate_all().
> +
> +	Therefore, it is important that DMA engine drivers drop any
> +	locks before calling the callback function which may cause a
> +	deadlock.
> +
> +	Note that callbacks will always be invoked from the DMA
> +	engines tasklet, never from interrupt context.
> +
> +4. Submit the transaction
> +
> +   Once the descriptor has been prepared and the callback information
> +   added, it must be placed on the DMA engine drivers pending queue.
> +
> +   Interface:
> +	dma_cookie_t dmaengine_submit(struct dma_async_tx_descriptor *desc)
> +
> +   This returns a cookie can be used to check the progress of DMA engine
> +   activity via other DMA engine calls not covered in this document.
> +
> +   dmaengine_submit() will not start the DMA operation, it merely adds
> +   it to the pending queue.  For this, see step 5, dma_async_issue_pending.
> +
> +5. Issue pending DMA requests and wait for callback notification
> +
> +   The transactions in the pending queue can be activated by calling the
> +   issue_pending API. If channel is idle then the first transaction in
> +   queue is started and subsequent ones queued up.
> +
> +   On completion of each DMA operation, the next in queue is started and
> +   a tasklet triggered. The tasklet will then call the client driver
> +   completion callback routine for notification, if set.
> +
> +   Interface:
> +	void dma_async_issue_pending(struct dma_chan *chan);
> +
> +Further APIs:
> +
> +1. int dmaengine_terminate_all(struct dma_chan *chan)
> +
> +   This causes all activity for the DMA channel to be stopped, and may
> +   discard data in the DMA FIFO which hasn't been fully transferred.
> +   No callback functions will be called for any incomplete transfers.
> +
> +2. int dmaengine_pause(struct dma_chan *chan)
> +
> +   This pauses activity on the DMA channel without data loss.
> +
> +3. int dmaengine_resume(struct dma_chan *chan)
> +
> +   Resume a previously paused DMA channel.  It is invalid to resume a
> +   channel which is not currently paused.
> +
> +4. enum dma_status dma_async_is_tx_complete(struct dma_chan *chan,
> +        dma_cookie_t cookie, dma_cookie_t *last, dma_cookie_t *used)
> +
> +   This can be used to check the status of the channel.  Please see
> +   the documentation in include/linux/dmaengine.h for a more complete
> +   description of this API.
> +
> +   This can be used in conjunction with dma_async_is_complete() and
> +   the cookie returned from dmaengine_submit() to check for
> +   completion of a specific DMA transaction.
> +
> +   Note:
> +	Not all DMA engine drivers can return reliable information for
> +	a running DMA channel.  It is recommended that DMA engine users
> +	pause or stop (via dmaengine_terminate_all) the channel before
> +	using this API.
> -- 
> 2.1.0
> 

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