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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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56
drivers/i2c/busses/i2c-virtio.c
View File

@ -62,35 +62,33 @@ static int virtio_i2c_prepare_reqs(struct virtqueue *vq,
for (i = 0; i < num; i++) {
int outcnt = 0, incnt = 0;
/*
* We don't support 0 length messages and so filter out
* 0 length transfers by using i2c_adapter_quirks.
*/
if (!msgs[i].len)
break;
/*
* Only 7-bit mode supported for this moment. For the address
* format, Please check the Virtio I2C Specification.
*/
reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);
if (msgs[i].flags & I2C_M_RD)
reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_M_RD);
if (i != num - 1)
reqs[i].out_hdr.flags = cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT);
reqs[i].out_hdr.flags |= cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT);
sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr));
sgs[outcnt++] = &out_hdr;
reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1);
if (!reqs[i].buf)
break;
if (msgs[i].len) {
reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1);
if (!reqs[i].buf)
break;
sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);
sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);
if (msgs[i].flags & I2C_M_RD)
sgs[outcnt + incnt++] = &msg_buf;
else
sgs[outcnt++] = &msg_buf;
if (msgs[i].flags & I2C_M_RD)
sgs[outcnt + incnt++] = &msg_buf;
else
sgs[outcnt++] = &msg_buf;
}
sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr));
sgs[outcnt + incnt++] = &in_hdr;
@ -191,7 +189,7 @@ static int virtio_i2c_setup_vqs(struct virtio_i2c *vi)
static u32 virtio_i2c_func(struct i2c_adapter *adap)
{
return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}
static struct i2c_algorithm virtio_algorithm = {
@ -199,15 +197,16 @@ static struct i2c_algorithm virtio_algorithm = {
.functionality = virtio_i2c_func,
};
static const struct i2c_adapter_quirks virtio_i2c_quirks = {
.flags = I2C_AQ_NO_ZERO_LEN,
};
static int virtio_i2c_probe(struct virtio_device *vdev)
{
struct virtio_i2c *vi;
int ret;
if (!virtio_has_feature(vdev, VIRTIO_I2C_F_ZERO_LENGTH_REQUEST)) {
dev_err(&vdev->dev, "Zero-length request feature is mandatory\n");
return -EINVAL;
}
vi = devm_kzalloc(&vdev->dev, sizeof(*vi), GFP_KERNEL);
if (!vi)
return -ENOMEM;
@ -225,7 +224,6 @@ static int virtio_i2c_probe(struct virtio_device *vdev)
snprintf(vi->adap.name, sizeof(vi->adap.name),
"i2c_virtio at virtio bus %d", vdev->index);
vi->adap.algo = &virtio_algorithm;
vi->adap.quirks = &virtio_i2c_quirks;
vi->adap.dev.parent = &vdev->dev;
vi->adap.dev.of_node = vdev->dev.of_node;
i2c_set_adapdata(&vi->adap, vi);
@ -270,11 +268,17 @@ static int virtio_i2c_restore(struct virtio_device *vdev)
}
#endif
static const unsigned int features[] = {
VIRTIO_I2C_F_ZERO_LENGTH_REQUEST,
};
static struct virtio_driver virtio_i2c_driver = {
.id_table = id_table,
.probe = virtio_i2c_probe,
.remove = virtio_i2c_remove,
.driver = {
.feature_table = features,
.feature_table_size = ARRAY_SIZE(features),
.id_table = id_table,
.probe = virtio_i2c_probe,
.remove = virtio_i2c_remove,
.driver = {
.name = "i2c_virtio",
},
#ifdef CONFIG_PM_SLEEP

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