Commit dcce1625 authored by Viresh Kumar's avatar Viresh Kumar Committed by Michael S. Tsirkin
Browse files

i2c: virtio: Add support for zero-length requests 



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: default avatarViresh Kumar <viresh.kumar@linaro.org>
Link: https://lore.kernel.org/r/7c58868cd26d2fc4bd82d0d8b0dfb55636380110.1634808714.git.viresh.kumar@linaro.org


Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Acked-by: Jie Deng <jie.deng@intel.com> # once the spec is merged
parent f1aa12f5

drivers/i2c/busses/i2c-virtio.c

+30 −26
Original line number Diff line number Diff line
@@ -62,25 +62,22 @@ 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;



		if (msgs[i].len) {

			reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1);

			if (!reqs[i].buf)

				break;
@@ -91,6 +88,7 @@ static int virtio_i2c_prepare_reqs(struct virtqueue *vq, 
				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);
@@ -270,7 +268,13 @@ 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 = {

	.feature_table		= features,

	.feature_table_size	= ARRAY_SIZE(features),

	.id_table		= id_table,

	.probe			= virtio_i2c_probe,

	.remove			= virtio_i2c_remove,

include/uapi/linux/virtio_i2c.h

+6 −0
Original line number Diff line number Diff line
@@ -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