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spi: core: added spi_resource management

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SPI resource management framework used while processing a spi_message
via the spi-core.

The basic idea is taken from devres, but as the allocation may happen
fairly frequently, some provisioning (in the form of an unused spi_device
pointer argument to spi_res_alloc) has been made so that at a later stage
we may implement reuse objects allocated earlier avoiding the repeated
allocation by keeping a cache of objects that we can reuse.

This framework can get used for:
* rewriting spi_messages
  * to fullfill alignment requirements of the spi_master HW
  * to fullfill transfer length requirements
    (e.g: transfers need to be less than 64k)
  * consolidate spi_messages with multiple transfers into a single transfer
  when the total transfer length is below a threshold.
* reimplement spi_unmap_buf without explicitly needing to check if it has
  been mapped

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Martin Sperl
2015-12-14 15:20:18 +00:00
committed by Mark Brown
parent 92e963f50f
commit d780c3711d
2 changed files with 127 additions and 0 deletions
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36
include/linux/spi/spi.h
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@@ -582,6 +582,37 @@ extern void spi_unregister_master(struct spi_master *master);
extern struct spi_master *spi_busnum_to_master(u16 busnum);
/*
* SPI resource management while processing a SPI message
*/
/**
* struct spi_res - spi resource management structure
* @entry: list entry
* @release: release code called prior to freeing this resource
* @data: extra data allocated for the specific use-case
*
* this is based on ideas from devres, but focused on life-cycle
* management during spi_message processing
*/
typedef void (*spi_res_release_t)(struct spi_master *master,
struct spi_message *msg,
void *res);
struct spi_res {
struct list_head entry;
spi_res_release_t release;
unsigned long long data[]; /* guarantee ull alignment */
};
extern void *spi_res_alloc(struct spi_device *spi,
spi_res_release_t release,
size_t size, gfp_t gfp);
extern void spi_res_add(struct spi_message *message, void *res);
extern void spi_res_free(void *res);
extern void spi_res_release(struct spi_master *master,
struct spi_message *message);
/*---------------------------------------------------------------------------*/
/*
@@ -720,6 +751,7 @@ struct spi_transfer {
* @status: zero for success, else negative errno
* @queue: for use by whichever driver currently owns the message
* @state: for use by whichever driver currently owns the message
* @resources: for resource management when the spi message is processed
*
* A @spi_message is used to execute an atomic sequence of data transfers,
* each represented by a struct spi_transfer. The sequence is "atomic"
@@ -766,11 +798,15 @@ struct spi_message {
*/
struct list_head queue;
void *state;
/* list of spi_res reources when the spi message is processed */
struct list_head resources;
};
static inline void spi_message_init_no_memset(struct spi_message *m)
{
INIT_LIST_HEAD(&m->transfers);
INIT_LIST_HEAD(&m->resources);
}
static inline void spi_message_init(struct spi_message *m)