Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752449AbdFOSbc (ORCPT ); Thu, 15 Jun 2017 14:31:32 -0400 Received: from sauhun.de ([88.99.104.3]:38205 "EHLO pokefinder.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752640AbdFOSa7 (ORCPT ); Thu, 15 Jun 2017 14:30:59 -0400 From: Wolfram Sang To: linux-i2c@vger.kernel.org Cc: linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org, Wolfram Sang , Wolfram Sang Subject: [PATCH 1/4] i2c: add helpers to ease DMA handling Date: Thu, 15 Jun 2017 20:30:36 +0200 Message-Id: <20170615183039.22925-2-wsa+renesas@sang-engineering.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170615183039.22925-1-wsa+renesas@sang-engineering.com> References: <20170615183039.22925-1-wsa+renesas@sang-engineering.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3189 Lines: 96 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 Signed-off-by: Wolfram Sang --- include/linux/i2c.h | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 72d0ece70ed30d..7204d38eaff07c 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -33,7 +33,10 @@ #include #include /* for Host Notify IRQ */ #include /* for struct device_node */ +#include #include /* for swab16 */ +#include +#include #include extern struct bus_type i2c_bus_type; @@ -764,6 +767,68 @@ static inline u8 i2c_8bit_addr_from_msg(const struct i2c_msg *msg) return (msg->addr << 1) | (msg->flags & I2C_M_RD ? 1 : 0); } +/** + * 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_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 + * + * Note: This function should only be called from process context! It uses + * helper functions which work on the 'current' task. + */ +static inline 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; +} + +/** + * 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. + */ +static inline void i2c_release_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); +} + 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