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i2c: virtio: Add support for zero-length requests

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The virtio specification received a new mandatory feature
(VIRTIO_I2C_F_ZERO_LENGTH_REQUEST) for zero length requests. Fail if the
feature isn't offered by the device.

For each read-request, set the VIRTIO_I2C_FLAGS_M_RD flag, as required
by the VIRTIO_I2C_F_ZERO_LENGTH_REQUEST feature.

This allows us to support zero length requests, like SMBUS Quick, where
the buffer need not be sent anymore.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lore.kernel.org/r/7c58868cd26d2fc4bd82d0d8b0dfb55636380110.1634808714.git.viresh.kumar@linaro.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jie Deng <jie.deng@intel.com> # once the spec is merged
This commit is contained in:
Viresh Kumar 2021-10-21 15:17:49 +05:30 • committed by Michael S. Tsirkin
parent f1aa12f535
commit dcce162559
2 changed files with 36 additions and 26 deletions
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6
include/uapi/linux/virtio_i2c.h
View file

@ -11,9 +11,15 @@
#include <linux/const.h>
#include <linux/types.h>
/* Virtio I2C Feature bits */
#define VIRTIO_I2C_F_ZERO_LENGTH_REQUEST 0
/* The bit 0 of the @virtio_i2c_out_hdr.@flags, used to group the requests */
#define VIRTIO_I2C_FLAGS_FAIL_NEXT _BITUL(0)
/* The bit 1 of the @virtio_i2c_out_hdr.@flags, used to mark a buffer as read */
#define VIRTIO_I2C_FLAGS_M_RD _BITUL(1)
/**
* struct virtio_i2c_out_hdr - the virtio I2C message OUT header
* @addr: the controlled device address