[4/4] mtd: provide helper to prepare buffers for DMA operations
Commit Message
Some NAND controller drivers are making use of DMA to transfer data from
the controller to the buffer passed by the MTD user.
Provide a generic mtd_map/unmap_buf() implementation to avoid open coded
(and sometime erroneous) implementations.
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
drivers/mtd/mtdcore.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/mtd/mtd.h | 25 +++++++++++++++++++
2 files changed, 91 insertions(+)
Comments
Hi Boris,
[auto build test ERROR on spi/for-next]
[also build test ERROR on v4.6-rc1 next-20160331]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]
url: https://github.com/0day-ci/linux/commits/Boris-Brezillon/scatterlist-sg_table-from-virtual-pointer/20160331-203118
base: https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi for-next
config: m32r-m32104ut_defconfig (attached as .config)
reproduce:
wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=m32r
All error/warnings (new ones prefixed by >>):
In file included from include/linux/mtd/super.h:17:0,
from fs/romfs/storage.c:13:
>> include/linux/mtd/mtd.h:426:10: error: expected ';', ',' or ')' before 'enum'
enum dma_data_direction dir)
^
include/linux/mtd/mtd.h: In function 'mtd_unmap_buf':
>> include/linux/mtd/mtd.h:434:2: warning: 'return' with a value, in function returning void
return -ENOTSUPP;
^
fs/romfs/storage.c: At top level:
include/linux/mtd/mtd.h:431:13: warning: 'mtd_unmap_buf' defined but not used [-Wunused-function]
static void mtd_unmap_buf(struct mtd_info *mtd, struct device *dev,
^
--
In file included from include/linux/mtd/super.h:17:0,
from fs/romfs/super.c:72:
>> include/linux/mtd/mtd.h:426:10: error: expected ';', ',' or ')' before 'enum'
enum dma_data_direction dir)
^
include/linux/mtd/mtd.h: In function 'mtd_unmap_buf':
>> include/linux/mtd/mtd.h:434:2: warning: 'return' with a value, in function returning void
return -ENOTSUPP;
^
fs/romfs/super.c: At top level:
include/linux/mtd/mtd.h:431:13: warning: 'mtd_unmap_buf' defined but not used [-Wunused-function]
static void mtd_unmap_buf(struct mtd_info *mtd, struct device *dev,
^
vim +426 include/linux/mtd/mtd.h
420 struct sg_table *sgt, enum dma_data_direction dir);
421 #else
422 static inline int mtd_map_buf(struct mtd_info *mtd, struct device *dev,
423 struct sg_table *sgt, const void *buf,
424 size_t len,
425 const struct sg_constraints *constraints
> 426 enum dma_data_direction dir)
427 {
428 return -ENOTSUPP;
429 }
430
431 static void mtd_unmap_buf(struct mtd_info *mtd, struct device *dev,
432 struct sg_table *sgt, enum dma_data_direction dir)
433 {
> 434 return -ENOTSUPP;
435 }
436 #endif
437
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
@@ -1253,6 +1253,72 @@ void *mtd_kmalloc_up_to(const struct mtd_info *mtd, size_t *size)
}
EXPORT_SYMBOL_GPL(mtd_kmalloc_up_to);
+#ifdef CONFIG_HAS_DMA
+/**
+ * mtd_map_buf - create an SG table and prepare it for DMA operations
+ *
+ * @mtd: mtd device description object pointer
+ * @dev: device handling the DMA operation
+ * @buf: buf used to create the SG table
+ * @len: length of buf
+ * @constraints: optional constraints to take into account when creating
+ * the SG table. Can be NULL if no specific constraints
+ * are required.
+ * @dir: direction of the DMA operation
+ *
+ * This function should be used when an MTD driver wants to do DMA operations
+ * on a buffer passed by the MTD layer. This functions takes care of
+ * vmallocated buffer constraints, and return and sg_table that you can safely
+ * use.
+ */
+int mtd_map_buf(struct mtd_info *mtd, struct device *dev,
+ struct sg_table *sgt, const void *buf, size_t len,
+ const struct sg_constraints *constraints,
+ enum dma_data_direction dir)
+{
+ int ret;
+
+ ret = sg_alloc_table_from_buf(sgt, buf, len, constraints, GFP_KERNEL);
+ if (ret)
+ return ret;
+
+ ret = dma_map_sg(dev, sgt->sgl, sgt->nents, dir);
+ if (!ret)
+ ret = -ENOMEM;
+
+ if (ret < 0) {
+ sg_free_table(sgt);
+ return ret;
+ }
+
+ sgt->nents = ret;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(mtd_map_buf);
+
+/**
+ * mtd_unmap_buf - unmap an SG table and release its resources
+ *
+ * @mtd: mtd device description object pointer
+ * @dev: device handling the DMA operation
+ * @sgt: SG table
+ * @dir: direction of the DMA operation
+ *
+ * This function unmaps a previously mapped SG table and release SG table
+ * resources. Should be called when your DMA operation is done.
+ */
+void mtd_unmap_buf(struct mtd_info *mtd, struct device *dev,
+ struct sg_table *sgt, enum dma_data_direction dir)
+{
+ if (sgt->orig_nents) {
+ dma_unmap_sg(dev, sgt->sgl, sgt->orig_nents, dir);
+ sg_free_table(sgt);
+ }
+}
+EXPORT_SYMBOL_GPL(mtd_unmap_buf);
+#endif /* !CONFIG_HAS_DMA */
+
#ifdef CONFIG_PROC_FS
/*====================================================================*/
@@ -24,6 +24,7 @@
#include <linux/uio.h>
#include <linux/notifier.h>
#include <linux/device.h>
+#include <linux/dma-mapping.h>
#include <mtd/mtd-abi.h>
@@ -410,6 +411,30 @@ extern void register_mtd_user (struct mtd_notifier *new);
extern int unregister_mtd_user (struct mtd_notifier *old);
void *mtd_kmalloc_up_to(const struct mtd_info *mtd, size_t *size);
+#ifdef CONFIG_HAS_DMA
+int mtd_map_buf(struct mtd_info *mtd, struct device *dev,
+ struct sg_table *sgt, const void *buf, size_t len,
+ const struct sg_constraints *constraints,
+ enum dma_data_direction dir);
+void mtd_unmap_buf(struct mtd_info *mtd, struct device *dev,
+ struct sg_table *sgt, enum dma_data_direction dir);
+#else
+static inline int mtd_map_buf(struct mtd_info *mtd, struct device *dev,
+ struct sg_table *sgt, const void *buf,
+ size_t len,
+ const struct sg_constraints *constraints
+ enum dma_data_direction dir)
+{
+ return -ENOTSUPP;
+}
+
+static void mtd_unmap_buf(struct mtd_info *mtd, struct device *dev,
+ struct sg_table *sgt, enum dma_data_direction dir)
+{
+ return -ENOTSUPP;
+}
+#endif
+
void mtd_erase_callback(struct erase_info *instr);
static inline int mtd_is_bitflip(int err) {