From: Wolfram Sang <wsa+renesas@sang-engineering.com>
To: linux-i2c@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-iio@vger.kernel.org, linux-input@vger.kernel.org,
linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
Wolfram Sang <wsa+renesas@sang-engineering.com>
Subject: [RFC PATCH v4 1/6] i2c: add a message flag for DMA safe buffers
Date: Thu, 17 Aug 2017 16:14:44 +0200 [thread overview]
Message-ID: <20170817141449.23958-2-wsa+renesas@sang-engineering.com> (raw)
In-Reply-To: <20170817141449.23958-1-wsa+renesas@sang-engineering.com>
I2C has no requirement that the buffer of a message needs to be DMA
safe. In case it is, it can now be flagged, so drivers wishing to
do DMA can use the buffer directly.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
include/uapi/linux/i2c.h | 3 +++
1 file changed, 3 insertions(+)
diff --git a/include/uapi/linux/i2c.h b/include/uapi/linux/i2c.h
index 009e27bb9abe19..1c683cb319e4b7 100644
--- a/include/uapi/linux/i2c.h
+++ b/include/uapi/linux/i2c.h
@@ -71,6 +71,9 @@ struct i2c_msg {
#define I2C_M_RD 0x0001 /* read data, from slave to master */
/* I2C_M_RD is guaranteed to be 0x0001! */
#define I2C_M_TEN 0x0010 /* this is a ten bit chip address */
+#define I2C_M_DMA_SAFE 0x0200 /* the buffer of this message is DMA safe */
+ /* makes only sense in kernelspace */
+ /* userspace buffers are copied anyway */
#define I2C_M_RECV_LEN 0x0400 /* length will be first received byte */
#define I2C_M_NO_RD_ACK 0x0800 /* if I2C_FUNC_PROTOCOL_MANGLING */
#define I2C_M_IGNORE_NAK 0x1000 /* if I2C_FUNC_PROTOCOL_MANGLING */
--
2.11.0
next prev parent reply other threads:[~2017-08-17 14:14 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-17 14:14 [RFC PATCH v4 0/6] i2c: document DMA handling and add helpers for it Wolfram Sang
2017-08-17 14:14 ` Wolfram Sang [this message]
2017-08-17 14:14 ` [RFC PATCH v4 2/6] i2c: add helpers to ease DMA handling Wolfram Sang
2017-08-17 14:14 ` [RFC PATCH v4 3/6] i2c: add docs to clarify " Wolfram Sang
2017-08-27 11:37 ` Mauro Carvalho Chehab
2017-09-08 8:56 ` Wolfram Sang
2017-09-08 11:08 ` Mauro Carvalho Chehab
2017-09-09 15:27 ` Wolfram Sang
2017-09-09 19:34 ` Mauro Carvalho Chehab
2017-09-20 17:18 ` Wolfram Sang
2017-09-20 18:22 ` Mauro Carvalho Chehab
2017-09-20 18:45 ` Wolfram Sang
2017-08-17 14:14 ` [RFC PATCH v4 4/6] i2c: sh_mobile: use helper to decide if DMA is useful Wolfram Sang
2017-08-17 14:14 ` [RFC PATCH v4 5/6] i2c: rcar: skip DMA if buffer is not safe Wolfram Sang
2017-08-17 14:14 ` [RFC PATCH v4 6/6] i2c: dev: mark RDWR buffers as DMA_SAFE Wolfram Sang
2017-08-20 10:14 ` [RFC PATCH v4 0/6] i2c: document DMA handling and add helpers for it Jonathan Cameron
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