i2c: Emulate SMBus block read over I2C

Let the I2C bus drivers emulate the SMBus Block Read and Block Process
Call transactions if they wish. This requires to define a new message
flag, which i2c-core will use to let the underlying I2C bus driver
know that the first received byte will specify the length of the read
message.

Signed-off-by: Jean Delvare <khali@linux-fr.org>

2 files changed, 27 insertions, 8 deletions

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index ae07b874a5d7..fd921ce0b75b 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -590,8 +590,9 @@ int i2c_transfer(struct i2c_adapter * adap, struct i2c_msg *msgs, int num)
 #ifdef DEBUG
                 for (ret = 0; ret < num; ret++) {
                         dev_dbg(&adap->dev, "master_xfer[%d] %c, addr=0x%02x, "
-                                "len=%d\n", ret, msgs[ret].flags & I2C_M_RD ?
-                                'R' : 'W', msgs[ret].addr, msgs[ret].len);
+                                "len=%d%s\n", ret, (msgs[ret].flags & I2C_M_RD)
+                                ? 'R' : 'W', msgs[ret].addr, msgs[ret].len,
+                                (msgs[ret].flags & I2C_M_RECV_LEN) ? "+" : "");
                 }
 #endif
 
@@ -1050,9 +1051,9 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
                 break;
         case I2C_SMBUS_BLOCK_DATA:
                 if (read_write == I2C_SMBUS_READ) {
-                        dev_err(&adapter->dev, "Block read not supported "
-                               "under I2C emulation!\n");
-                        return -1;
+                        msg[1].flags |= I2C_M_RECV_LEN;
+                        msg[1].len = 1; /* block length will be added by
+                                           the underlying bus driver */
                 } else {
                         msg[0].len = data->block[0] + 2;
                         if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 2) {
@@ -1066,9 +1067,21 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
                 }
                 break;
         case I2C_SMBUS_BLOCK_PROC_CALL:
-                dev_dbg(&adapter->dev, "Block process call not supported "
-                       "under I2C emulation!\n");
-                return -1;
+                num = 2; /* Another special case */
+                read_write = I2C_SMBUS_READ;
+                if (data->block[0] > I2C_SMBUS_BLOCK_MAX) {
+                        dev_err(&adapter->dev, "%s called with invalid "
+                                "block proc call size (%d)\n", __FUNCTION__,
+                                data->block[0]);
+                        return -1;
+                }
+                msg[0].len = data->block[0] + 2;
+                for (i = 1; i < msg[0].len; i++)
+                        msgbuf0[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 */
+                break;
         case I2C_SMBUS_I2C_BLOCK_DATA:
                 if (read_write == I2C_SMBUS_READ) {
                         msg[1].len = I2C_SMBUS_BLOCK_MAX;
@@ -1132,6 +1145,11 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
                                 for (i = 0; i < I2C_SMBUS_BLOCK_MAX; i++)
                                         data->block[i+1] = msgbuf1[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];
+                                break;
                 }
         return 0;
 }
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 568dd1007b53..563c9651dd37 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -366,6 +366,7 @@ struct i2c_msg {
 #define I2C_M_REV_DIR_ADDR      0x2000
 #define I2C_M_IGNORE_NAK        0x1000
 #define I2C_M_NO_RD_ACK         0x0800
+#define I2C_M_RECV_LEN          0x0400 /* length will be first received byte */
         __u16 len;              /* msg length                           */
         __u8 *buf;              /* pointer to msg data                  */
 };