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Commit 8a77821e authored by Wolfram Sang's avatar Wolfram Sang Committed by Wolfram Sang
Browse files

i2c: smbus: use DMA safe buffers for emulated SMBus transactions 



For all block commands, try to allocate a DMA safe buffer and mark it
accordingly. Only use the stack, if the buffers cannot be allocated.

Signed-off-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent ba98645c

drivers/i2c/i2c-core-smbus.c

+39 −6
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <linux/err.h>

#include <linux/i2c.h>

#include <linux/i2c-smbus.h>

#include <linux/slab.h>



#define CREATE_TRACE_POINTS

#include <trace/events/smbus.h>
@@ -291,6 +292,22 @@ s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, u8 command, 
}

EXPORT_SYMBOL(i2c_smbus_write_i2c_block_data);



static void i2c_smbus_try_get_dmabuf(struct i2c_msg *msg, u8 init_val)

{

	bool is_read = msg->flags & I2C_M_RD;

	unsigned char *dma_buf;



	dma_buf = kzalloc(I2C_SMBUS_BLOCK_MAX + (is_read ? 2 : 3), GFP_KERNEL);

	if (!dma_buf)

		return;



	msg->buf = dma_buf;

	msg->flags |= I2C_M_DMA_SAFE;



	if (init_val)

		msg->buf[0] = init_val;

}



/* Simulate a SMBus command using the i2c protocol

   No checking of parameters is done!  */

static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
@@ -368,6 +385,7 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr, 
			msg[1].flags |= I2C_M_RECV_LEN;

			msg[1].len = 1; /* block length will be added by

					   the underlying bus driver */

			i2c_smbus_try_get_dmabuf(&msg[1], 0);

		} else {

			msg[0].len = data->block[0] + 2;

			if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 2) {
@@ -376,8 +394,10 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr, 
					data->block[0]);

				return -EINVAL;

			}



			i2c_smbus_try_get_dmabuf(&msg[0], command);

			for (i = 1; i < msg[0].len; i++)

				msgbuf0[i] = data->block[i-1];

				msg[0].buf[i] = data->block[i - 1];

		}

		break;

	case I2C_SMBUS_BLOCK_PROC_CALL:
@@ -389,16 +409,21 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr, 
				data->block[0]);

			return -EINVAL;

		}



		msg[0].len = data->block[0] + 2;

		i2c_smbus_try_get_dmabuf(&msg[0], command);

		for (i = 1; i < msg[0].len; i++)

			msgbuf0[i] = data->block[i-1];

			msg[0].buf[i] = data->block[i - 1];



		msg[1].flags |= I2C_M_RECV_LEN;

		msg[1].len = 1; /* block length will be added by

				   the underlying bus driver */

		i2c_smbus_try_get_dmabuf(&msg[1], 0);

		break;

	case I2C_SMBUS_I2C_BLOCK_DATA:

		if (read_write == I2C_SMBUS_READ) {

			msg[1].len = data->block[0];

			i2c_smbus_try_get_dmabuf(&msg[1], 0);

		} else {

			msg[0].len = data->block[0] + 1;

			if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 1) {
@@ -407,8 +432,10 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr, 
					data->block[0]);

				return -EINVAL;

			}



			i2c_smbus_try_get_dmabuf(&msg[0], command);

			for (i = 1; i <= data->block[0]; i++)

				msgbuf0[i] = data->block[i];

				msg[0].buf[i] = data->block[i];

		}

		break;

	default:
@@ -456,14 +483,20 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr, 
			break;

		case I2C_SMBUS_I2C_BLOCK_DATA:

			for (i = 0; i < data->block[0]; i++)

				data->block[i+1] = msgbuf1[i];

				data->block[i + 1] = msg[1].buf[i];

			break;

		case I2C_SMBUS_BLOCK_DATA:

		case I2C_SMBUS_BLOCK_PROC_CALL:

			for (i = 0; i < msgbuf1[0] + 1; i++)

				data->block[i] = msgbuf1[i];

			for (i = 0; i < msg[1].buf[0] + 1; i++)

				data->block[i] = msg[1].buf[i];

			break;

		}



	if (msg[0].flags & I2C_M_DMA_SAFE)

		kfree(msg[0].buf);

	if (msg[1].flags & I2C_M_DMA_SAFE)

		kfree(msg[1].buf);



	return 0;

}