Hi Wolfram,
On 2017-07-18 12:23:36 +0200, Wolfram Sang wrote:
One helper checks if DMA is suitable and optionally creates a bounce buffer, if not. The other function returns the bounce buffer and makes sure the data is properly copied back to the message.
Signed-off-by: Wolfram Sang wsa+renesas@sang-engineering.com
Reviewed-by: Niklas Söderlund niklas.soderlund+renesas@ragnatech.se
Changes since v2:
- rebased to v4.13-rc1
- helper functions are not inlined anymore but moved to i2c core
- __must_check has been added to the buffer check helper
- the release function has been renamed to contain 'dma' as well
drivers/i2c/i2c-core-base.c | 68 +++++++++++++++++++++++++++++++++++++++++++++ include/linux/i2c.h | 5 ++++ 2 files changed, 73 insertions(+)
diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c index c89dac7fd2e7b7..7326a9d2e4eb69 100644 --- a/drivers/i2c/i2c-core-base.c +++ b/drivers/i2c/i2c-core-base.c @@ -34,6 +34,7 @@ #include <linux/irqflags.h> #include <linux/jump_label.h> #include <linux/kernel.h> +#include <linux/mm.h> #include <linux/module.h> #include <linux/mutex.h> #include <linux/of_device.h> @@ -44,6 +45,7 @@ #include <linux/pm_wakeirq.h> #include <linux/property.h> #include <linux/rwsem.h> +#include <linux/sched/task_stack.h> #include <linux/slab.h>
#include "i2c-core.h" @@ -2240,6 +2242,72 @@ void i2c_put_adapter(struct i2c_adapter *adap) } EXPORT_SYMBOL(i2c_put_adapter);
+/**
- i2c_check_msg_for_dma() - check if a message is suitable for DMA
- @msg: the message to be checked
- @threshold: the amount of byte from which using DMA makes sense
- @ptr_for_bounce_buf: if not NULL, a bounce buffer will be attached to this
ptr, if needed. The bounce buffer must be freed by the
caller using i2c_release_dma_bounce_buf().
- Return: -ERANGE if message is smaller than threshold
-EFAULT if message buffer is not DMA capable and no bounce buffer
was requested
-ENOMEM if a bounce buffer could not be created
0 if message is suitable for DMA
- The return value must be checked.
- Note: This function should only be called from process context! It uses
- helper functions which work on the 'current' task.
- */
+int i2c_check_msg_for_dma(struct i2c_msg *msg, unsigned int threshold,
u8 **ptr_for_bounce_buf)+{
- if (ptr_for_bounce_buf)
*ptr_for_bounce_buf = NULL;- if (msg->len < threshold)
return -ERANGE;- if (!virt_addr_valid(msg->buf) || object_is_on_stack(msg->buf)) {
pr_debug("msg buffer to 0x%04x is not DMA safe%s\n", msg->addr,ptr_for_bounce_buf ? ", trying bounce buffer" : "");if (ptr_for_bounce_buf) {if (msg->flags & I2C_M_RD)*ptr_for_bounce_buf = kzalloc(msg->len, GFP_KERNEL);else*ptr_for_bounce_buf = kmemdup(msg->buf, msg->len,GFP_KERNEL);if (!*ptr_for_bounce_buf)return -ENOMEM;} else {return -EFAULT;}- }
- return 0;
+} +EXPORT_SYMBOL_GPL(i2c_check_msg_for_dma);
+/**
- i2c_release_bounce_buf - copy data back from bounce buffer and release it
- @msg: the message to be copied back to
- @bounce_buf: the bounce buffer obtained from i2c_check_msg_for_dma().
May be NULL.- */
+void i2c_release_dma_bounce_buf(struct i2c_msg *msg, u8 *bounce_buf) +{
- if (!bounce_buf)
return;- if (msg->flags & I2C_M_RD)
memcpy(msg->buf, bounce_buf, msg->len);- kfree(bounce_buf);
+} +EXPORT_SYMBOL_GPL(i2c_release_bounce_buf);
MODULE_AUTHOR("Simon G. Vogl simon@tk.uni-linz.ac.at"); MODULE_DESCRIPTION("I2C-Bus main module"); MODULE_LICENSE("GPL"); diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 00ca5b86a753f8..ac02287b6c0d8f 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -766,6 +766,11 @@ static inline u8 i2c_8bit_addr_from_msg(const struct i2c_msg *msg) return (msg->addr << 1) | (msg->flags & I2C_M_RD ? 1 : 0); }
+int __must_check i2c_check_msg_for_dma(struct i2c_msg *msg, unsigned int threshold,
u8 **ptr_for_bounce_buf);+void i2c_release_dma_bounce_buf(struct i2c_msg *msg, u8 *bounce_buf);
int i2c_handle_smbus_host_notify(struct i2c_adapter *adap, unsigned short addr); /**
- module_i2c_driver() - Helper macro for registering a modular I2C driver
-- 2.11.0