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Commit e94bc5d1 authored by Wolfram Sang's avatar Wolfram Sang Committed by Wolfram Sang
Browse files

i2c: add helpers to ease DMA handling 



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.

Reviewed-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent 521a72e1

drivers/i2c/i2c-core-base.c

+46 −0
Original line number Diff line number Diff line
@@ -2200,6 +2200,52 @@ void i2c_put_adapter(struct i2c_adapter *adap) 
}

EXPORT_SYMBOL(i2c_put_adapter);



/**

 * i2c_get_dma_safe_msg_buf() - get a DMA safe buffer for the given i2c_msg

 * @msg: the message to be checked

 * @threshold: the minimum number of bytes for which using DMA makes sense

 *

 * Return: NULL if a DMA safe buffer was not obtained. Use msg->buf with PIO.

 *	   Or a valid pointer to be used with DMA. After use, release it by

 *	   calling i2c_release_dma_safe_msg_buf().

 *

 * This function must only be called from process context!

 */

u8 *i2c_get_dma_safe_msg_buf(struct i2c_msg *msg, unsigned int threshold)

{

	if (msg->len < threshold)

		return NULL;



	if (msg->flags & I2C_M_DMA_SAFE)

		return msg->buf;



	pr_debug("using bounce buffer for addr=0x%02x, len=%d\n",

		 msg->addr, msg->len);



	if (msg->flags & I2C_M_RD)

		return kzalloc(msg->len, GFP_KERNEL);

	else

		return kmemdup(msg->buf, msg->len, GFP_KERNEL);

}

EXPORT_SYMBOL_GPL(i2c_get_dma_safe_msg_buf);



/**

 * i2c_release_dma_safe_msg_buf - release DMA safe buffer and sync with i2c_msg

 * @msg: the message to be synced with

 * @buf: the buffer obtained from i2c_get_dma_safe_msg_buf(). May be NULL.

 */

void i2c_release_dma_safe_msg_buf(struct i2c_msg *msg, u8 *buf)

{

	if (!buf || buf == msg->buf)

		return;



	if (msg->flags & I2C_M_RD)

		memcpy(msg->buf, buf, msg->len);



	kfree(buf);

}

EXPORT_SYMBOL_GPL(i2c_release_dma_safe_msg_buf);



MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");

MODULE_DESCRIPTION("I2C-Bus main module");

MODULE_LICENSE("GPL");

include/linux/i2c.h

+3 −0
Original line number Diff line number Diff line
@@ -768,6 +768,9 @@ static inline u8 i2c_8bit_addr_from_msg(const struct i2c_msg *msg) 
	return (msg->addr << 1) | (msg->flags & I2C_M_RD ? 1 : 0);

}



u8 *i2c_get_dma_safe_msg_buf(struct i2c_msg *msg, unsigned int threshold);

void i2c_release_dma_safe_msg_buf(struct i2c_msg *msg, u8 *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