[PATCH] SPI core tweaks, bugfix
This includes various updates to the SPI core:
- Fixes a driver model refcount bug in spi_unregister_master() paths.
- The spi_master structures now have wrappers which help keep drivers
from needing class-level get/put for device data or for refcounts.
- Check for a few setup errors that would cause oopsing later.
- Docs say more about memory management. Highlights the use of DMA-safe
i/o buffers, and zero-initializing spi_message and such metadata.
- Provide a simple alloc/free for spi_message and its spi_transfer;
this is only one of the possible memory management policies.
Nothing to break code that already works.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
David Brownell
Greg Kroah-Hartman
parent
b885244eb2
commit
0c868461fc
|
|
@ -363,6 +363,22 @@ upper boundaries might include sysfs (especially for sensor readings),
|
|||
the input layer, ALSA, networking, MTD, the character device framework,
|
||||
or other Linux subsystems.
|
||||
|
||||
Note that there are two types of memory your driver must manage as part
|
||||
of interacting with SPI devices.
|
||||
|
||||
- I/O buffers use the usual Linux rules, and must be DMA-safe.
|
||||
You'd normally allocate them from the heap or free page pool.
|
||||
Don't use the stack, or anything that's declared "static".
|
||||
|
||||
- The spi_message and spi_transfer metadata used to glue those
|
||||
I/O buffers into a group of protocol transactions. These can
|
||||
be allocated anywhere it's convenient, including as part of
|
||||
other allocate-once driver data structures. Zero-init these.
|
||||
|
||||
If you like, spi_message_alloc() and spi_message_free() convenience
|
||||
routines are available to allocate and zero-initialize an spi_message
|
||||
with several transfers.
|
||||
|
||||
|
||||
How do I write an "SPI Master Controller Driver"?
|
||||
-------------------------------------------------
|
||||
|
|
|
|||
|
|
@ -38,7 +38,7 @@ static void spidev_release(struct device *dev)
|
|||
if (spi->master->cleanup)
|
||||
spi->master->cleanup(spi);
|
||||
|
||||
class_device_put(&spi->master->cdev);
|
||||
spi_master_put(spi->master);
|
||||
kfree(dev);
|
||||
}
|
||||
|
||||
|
|
@ -90,7 +90,7 @@ static int spi_suspend(struct device *dev, pm_message_t message)
|
|||
int value;
|
||||
struct spi_driver *drv = to_spi_driver(dev->driver);
|
||||
|
||||
if (!drv || !drv->suspend)
|
||||
if (!drv->suspend)
|
||||
return 0;
|
||||
|
||||
/* suspend will stop irqs and dma; no more i/o */
|
||||
|
|
@ -105,7 +105,7 @@ static int spi_resume(struct device *dev)
|
|||
int value;
|
||||
struct spi_driver *drv = to_spi_driver(dev->driver);
|
||||
|
||||
if (!drv || !drv->resume)
|
||||
if (!drv->resume)
|
||||
return 0;
|
||||
|
||||
/* resume may restart the i/o queue */
|
||||
|
|
@ -198,7 +198,7 @@ spi_new_device(struct spi_master *master, struct spi_board_info *chip)
|
|||
|
||||
/* NOTE: caller did any chip->bus_num checks necessary */
|
||||
|
||||
if (!class_device_get(&master->cdev))
|
||||
if (!spi_master_get(master))
|
||||
return NULL;
|
||||
|
||||
proxy = kzalloc(sizeof *proxy, GFP_KERNEL);
|
||||
|
|
@ -244,7 +244,7 @@ spi_new_device(struct spi_master *master, struct spi_board_info *chip)
|
|||
return proxy;
|
||||
|
||||
fail:
|
||||
class_device_put(&master->cdev);
|
||||
spi_master_put(master);
|
||||
kfree(proxy);
|
||||
return NULL;
|
||||
}
|
||||
|
|
@ -324,8 +324,6 @@ static void spi_master_release(struct class_device *cdev)
|
|||
struct spi_master *master;
|
||||
|
||||
master = container_of(cdev, struct spi_master, cdev);
|
||||
put_device(master->cdev.dev);
|
||||
master->cdev.dev = NULL;
|
||||
kfree(master);
|
||||
}
|
||||
|
||||
|
|
@ -339,8 +337,9 @@ static struct class spi_master_class = {
|
|||
/**
|
||||
* spi_alloc_master - allocate SPI master controller
|
||||
* @dev: the controller, possibly using the platform_bus
|
||||
* @size: how much driver-private data to preallocate; a pointer to this
|
||||
* memory in the class_data field of the returned class_device
|
||||
* @size: how much driver-private data to preallocate; the pointer to this
|
||||
* memory is in the class_data field of the returned class_device,
|
||||
* accessible with spi_master_get_devdata().
|
||||
*
|
||||
* This call is used only by SPI master controller drivers, which are the
|
||||
* only ones directly touching chip registers. It's how they allocate
|
||||
|
|
@ -350,14 +349,17 @@ static struct class spi_master_class = {
|
|||
* master structure on success, else NULL.
|
||||
*
|
||||
* The caller is responsible for assigning the bus number and initializing
|
||||
* the master's methods before calling spi_add_master(), or else (on error)
|
||||
* calling class_device_put() to prevent a memory leak.
|
||||
* the master's methods before calling spi_add_master(); and (after errors
|
||||
* adding the device) calling spi_master_put() to prevent a memory leak.
|
||||
*/
|
||||
struct spi_master * __init_or_module
|
||||
spi_alloc_master(struct device *dev, unsigned size)
|
||||
{
|
||||
struct spi_master *master;
|
||||
|
||||
if (!dev)
|
||||
return NULL;
|
||||
|
||||
master = kzalloc(size + sizeof *master, SLAB_KERNEL);
|
||||
if (!master)
|
||||
return NULL;
|
||||
|
|
@ -365,7 +367,7 @@ spi_alloc_master(struct device *dev, unsigned size)
|
|||
class_device_initialize(&master->cdev);
|
||||
master->cdev.class = &spi_master_class;
|
||||
master->cdev.dev = get_device(dev);
|
||||
class_set_devdata(&master->cdev, &master[1]);
|
||||
spi_master_set_devdata(master, &master[1]);
|
||||
|
||||
return master;
|
||||
}
|
||||
|
|
@ -387,6 +389,8 @@ EXPORT_SYMBOL_GPL(spi_alloc_master);
|
|||
*
|
||||
* This must be called from context that can sleep. It returns zero on
|
||||
* success, else a negative error code (dropping the master's refcount).
|
||||
* After a successful return, the caller is responsible for calling
|
||||
* spi_unregister_master().
|
||||
*/
|
||||
int __init_or_module
|
||||
spi_register_master(struct spi_master *master)
|
||||
|
|
@ -396,6 +400,9 @@ spi_register_master(struct spi_master *master)
|
|||
int status = -ENODEV;
|
||||
int dynamic = 0;
|
||||
|
||||
if (!dev)
|
||||
return -ENODEV;
|
||||
|
||||
/* convention: dynamically assigned bus IDs count down from the max */
|
||||
if (master->bus_num == 0) {
|
||||
master->bus_num = atomic_dec_return(&dyn_bus_id);
|
||||
|
|
@ -425,7 +432,7 @@ EXPORT_SYMBOL_GPL(spi_register_master);
|
|||
static int __unregister(struct device *dev, void *unused)
|
||||
{
|
||||
/* note: before about 2.6.14-rc1 this would corrupt memory: */
|
||||
device_unregister(dev);
|
||||
spi_unregister_device(to_spi_device(dev));
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
|
@ -440,8 +447,9 @@ static int __unregister(struct device *dev, void *unused)
|
|||
*/
|
||||
void spi_unregister_master(struct spi_master *master)
|
||||
{
|
||||
class_device_unregister(&master->cdev);
|
||||
(void) device_for_each_child(master->cdev.dev, NULL, __unregister);
|
||||
class_device_unregister(&master->cdev);
|
||||
master->cdev.dev = NULL;
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(spi_unregister_master);
|
||||
|
||||
|
|
@ -487,6 +495,9 @@ EXPORT_SYMBOL_GPL(spi_busnum_to_master);
|
|||
* by leaving it selected in anticipation that the next message will go
|
||||
* to the same chip. (That may increase power usage.)
|
||||
*
|
||||
* Also, the caller is guaranteeing that the memory associated with the
|
||||
* message will not be freed before this call returns.
|
||||
*
|
||||
* The return value is a negative error code if the message could not be
|
||||
* submitted, else zero. When the value is zero, then message->status is
|
||||
* also defined: it's the completion code for the transfer, either zero
|
||||
|
|
@ -524,9 +535,9 @@ static u8 *buf;
|
|||
* is zero for success, else a negative errno status code.
|
||||
* This call may only be used from a context that may sleep.
|
||||
*
|
||||
* Parameters to this routine are always copied using a small buffer,
|
||||
* large transfers should use use spi_{async,sync}() calls with
|
||||
* dma-safe buffers.
|
||||
* Parameters to this routine are always copied using a small buffer;
|
||||
* performance-sensitive or bulk transfer code should instead use
|
||||
* spi_{async,sync}() calls with dma-safe buffers.
|
||||
*/
|
||||
int spi_write_then_read(struct spi_device *spi,
|
||||
const u8 *txbuf, unsigned n_tx,
|
||||
|
|
|
|||
|
|
@ -60,8 +60,8 @@ struct spi_device {
|
|||
u8 mode;
|
||||
#define SPI_CPHA 0x01 /* clock phase */
|
||||
#define SPI_CPOL 0x02 /* clock polarity */
|
||||
#define SPI_MODE_0 (0|0)
|
||||
#define SPI_MODE_1 (0|SPI_CPHA) /* (original MicroWire) */
|
||||
#define SPI_MODE_0 (0|0) /* (original MicroWire) */
|
||||
#define SPI_MODE_1 (0|SPI_CPHA)
|
||||
#define SPI_MODE_2 (SPI_CPOL|0)
|
||||
#define SPI_MODE_3 (SPI_CPOL|SPI_CPHA)
|
||||
#define SPI_CS_HIGH 0x04 /* chipselect active high? */
|
||||
|
|
@ -209,6 +209,30 @@ struct spi_master {
|
|||
void (*cleanup)(const struct spi_device *spi);
|
||||
};
|
||||
|
||||
static inline void *spi_master_get_devdata(struct spi_master *master)
|
||||
{
|
||||
return class_get_devdata(&master->cdev);
|
||||
}
|
||||
|
||||
static inline void spi_master_set_devdata(struct spi_master *master, void *data)
|
||||
{
|
||||
class_set_devdata(&master->cdev, data);
|
||||
}
|
||||
|
||||
static inline struct spi_master *spi_master_get(struct spi_master *master)
|
||||
{
|
||||
if (!master || !class_device_get(&master->cdev))
|
||||
return NULL;
|
||||
return master;
|
||||
}
|
||||
|
||||
static inline void spi_master_put(struct spi_master *master)
|
||||
{
|
||||
if (master)
|
||||
class_device_put(&master->cdev);
|
||||
}
|
||||
|
||||
|
||||
/* the spi driver core manages memory for the spi_master classdev */
|
||||
extern struct spi_master *
|
||||
spi_alloc_master(struct device *host, unsigned size);
|
||||
|
|
@ -271,11 +295,17 @@ extern struct spi_master *spi_busnum_to_master(u16 busnum);
|
|||
* stay selected until the next transfer. This is purely a performance
|
||||
* hint; the controller driver may need to select a different device
|
||||
* for the next message.
|
||||
*
|
||||
* The code that submits an spi_message (and its spi_transfers)
|
||||
* to the lower layers is responsible for managing its memory.
|
||||
* Zero-initialize every field you don't set up explicitly, to
|
||||
* insulate against future API updates.
|
||||
*/
|
||||
struct spi_transfer {
|
||||
/* it's ok if tx_buf == rx_buf (right?)
|
||||
* for MicroWire, one buffer must be null
|
||||
* buffers must work with dma_*map_single() calls
|
||||
* buffers must work with dma_*map_single() calls, unless
|
||||
* spi_message.is_dma_mapped reports a pre-existing mapping
|
||||
*/
|
||||
const void *tx_buf;
|
||||
void *rx_buf;
|
||||
|
|
@ -302,6 +332,11 @@ 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
|
||||
*
|
||||
* The code that submits an spi_message (and its spi_transfers)
|
||||
* to the lower layers is responsible for managing its memory.
|
||||
* Zero-initialize every field you don't set up explicitly, to
|
||||
* insulate against future API updates.
|
||||
*/
|
||||
struct spi_message {
|
||||
struct spi_transfer *transfers;
|
||||
|
|
@ -336,6 +371,29 @@ struct spi_message {
|
|||
void *state;
|
||||
};
|
||||
|
||||
/* It's fine to embed message and transaction structures in other data
|
||||
* structures so long as you don't free them while they're in use.
|
||||
*/
|
||||
|
||||
static inline struct spi_message *spi_message_alloc(unsigned ntrans, gfp_t flags)
|
||||
{
|
||||
struct spi_message *m;
|
||||
|
||||
m = kzalloc(sizeof(struct spi_message)
|
||||
+ ntrans * sizeof(struct spi_transfer),
|
||||
flags);
|
||||
if (m) {
|
||||
m->transfers = (void *)(m + 1);
|
||||
m->n_transfer = ntrans;
|
||||
}
|
||||
return m;
|
||||
}
|
||||
|
||||
static inline void spi_message_free(struct spi_message *m)
|
||||
{
|
||||
kfree(m);
|
||||
}
|
||||
|
||||
/**
|
||||
* spi_setup -- setup SPI mode and clock rate
|
||||
* @spi: the device whose settings are being modified
|
||||
|
|
@ -363,7 +421,10 @@ spi_setup(struct spi_device *spi)
|
|||
* The completion callback is invoked in a context which can't sleep.
|
||||
* Before that invocation, the value of message->status is undefined.
|
||||
* When the callback is issued, message->status holds either zero (to
|
||||
* indicate complete success) or a negative error code.
|
||||
* indicate complete success) or a negative error code. After that
|
||||
* callback returns, the driver which issued the transfer request may
|
||||
* deallocate the associated memory; it's no longer in use by any SPI
|
||||
* core or controller driver code.
|
||||
*
|
||||
* Note that although all messages to a spi_device are handled in
|
||||
* FIFO order, messages may go to different devices in other orders.
|
||||
|
|
@ -445,6 +506,7 @@ spi_read(struct spi_device *spi, u8 *buf, size_t len)
|
|||
return spi_sync(spi, &m);
|
||||
}
|
||||
|
||||
/* this copies txbuf and rxbuf data; for small transfers only! */
|
||||
extern int spi_write_then_read(struct spi_device *spi,
|
||||
const u8 *txbuf, unsigned n_tx,
|
||||
u8 *rxbuf, unsigned n_rx);
|
||||
|
|
@ -555,8 +617,9 @@ spi_register_board_info(struct spi_board_info const *info, unsigned n)
|
|||
|
||||
|
||||
/* If you're hotplugging an adapter with devices (parport, usb, etc)
|
||||
* use spi_new_device() to describe each device. You would then call
|
||||
* spi_unregister_device() to start making that device vanish.
|
||||
* use spi_new_device() to describe each device. You can also call
|
||||
* spi_unregister_device() to start making that device vanish, but
|
||||
* normally that would be handled by spi_unregister_master().
|
||||
*/
|
||||
extern struct spi_device *
|
||||
spi_new_device(struct spi_master *, struct spi_board_info *);
|
||||
|
|
|
|||
Loading…
Reference in New Issue