From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sauhun.de ([88.99.104.3]:44794 "EHLO pokefinder.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751580AbdKDUUY (ORCPT ); Sat, 4 Nov 2017 16:20:24 -0400 From: Wolfram Sang To: linux-i2c@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-iio@vger.kernel.org, linux-input@vger.kernel.org, linux-media@vger.kernel.org, Mark Brown , Wolfram Sang , Jonathan Cameron Subject: [PATCH v6 2/9] i2c: add helpers to ease DMA handling Date: Sat, 4 Nov 2017 21:20:02 +0100 Message-Id: <20171104202009.3818-3-wsa+renesas@sang-engineering.com> In-Reply-To: <20171104202009.3818-1-wsa+renesas@sang-engineering.com> References: <20171104202009.3818-1-wsa+renesas@sang-engineering.com> Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org 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: Jonathan Cameron Signed-off-by: Wolfram Sang --- drivers/i2c/i2c-core-base.c | 46 +++++++++++++++++++++++++++++++++++++++++++++ include/linux/i2c.h | 3 +++ 2 files changed, 49 insertions(+) diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c index 706164b4c5be46..de1850bd440659 100644 --- a/drivers/i2c/i2c-core-base.c +++ b/drivers/i2c/i2c-core-base.c @@ -2261,6 +2261,52 @@ 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 "); MODULE_DESCRIPTION("I2C-Bus main module"); MODULE_LICENSE("GPL"); diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 0f774406fad0e4..a0b57de91e21d3 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -769,6 +769,9 @@ 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 -- 2.11.0