From 5f272644464bfb8cf8cec958cfc06020283c2f14 Mon Sep 17 00:00:00 2001 From: Andy Walls Date: Sun, 18 Jul 2010 17:16:16 -0300 Subject: [PATCH] V4L/DVB: cx25840: Make cx25840 i2c register read transactions atomic There was a small window between writing the cx25840 register address over the i2c bus and reading the register contents back from the cx25840 device that the i2c adapter lock was released. This change ensures the adapter lock is not released until the register read is done. Signed-off-by: Andy Walls Signed-off-by: Mauro Carvalho Chehab --- drivers/media/video/cx25840/cx25840-core.c | 58 ++++++++++++++++++++---------- 1 file changed, 39 insertions(+), 19 deletions(-) diff --git a/drivers/media/video/cx25840/cx25840-core.c b/drivers/media/video/cx25840/cx25840-core.c index bb4872b2ceb0..4f908fa4da08 100644 --- a/drivers/media/video/cx25840/cx25840-core.c +++ b/drivers/media/video/cx25840/cx25840-core.c @@ -80,33 +80,53 @@ int cx25840_write4(struct i2c_client *client, u16 addr, u32 value) u8 cx25840_read(struct i2c_client * client, u16 addr) { - u8 buffer[2]; - buffer[0] = addr >> 8; - buffer[1] = addr & 0xff; - - if (i2c_master_send(client, buffer, 2) < 2) - return 0; - - if (i2c_master_recv(client, buffer, 1) < 1) + struct i2c_msg msgs[2]; + u8 tx_buf[2], rx_buf[1]; + + /* Write register address */ + tx_buf[0] = addr >> 8; + tx_buf[1] = addr & 0xff; + msgs[0].addr = client->addr; + msgs[0].flags = 0; + msgs[0].len = 2; + msgs[0].buf = (char *) tx_buf; + + /* Read data from register */ + msgs[1].addr = client->addr; + msgs[1].flags = I2C_M_RD; + msgs[1].len = 1; + msgs[1].buf = (char *) rx_buf; + + if (i2c_transfer(client->adapter, msgs, 2) < 2) return 0; - return buffer[0]; + return rx_buf[0]; } u32 cx25840_read4(struct i2c_client * client, u16 addr) { - u8 buffer[4]; - buffer[0] = addr >> 8; - buffer[1] = addr & 0xff; - - if (i2c_master_send(client, buffer, 2) < 2) - return 0; - - if (i2c_master_recv(client, buffer, 4) < 4) + struct i2c_msg msgs[2]; + u8 tx_buf[2], rx_buf[4]; + + /* Write register address */ + tx_buf[0] = addr >> 8; + tx_buf[1] = addr & 0xff; + msgs[0].addr = client->addr; + msgs[0].flags = 0; + msgs[0].len = 2; + msgs[0].buf = (char *) tx_buf; + + /* Read data from registers */ + msgs[1].addr = client->addr; + msgs[1].flags = I2C_M_RD; + msgs[1].len = 4; + msgs[1].buf = (char *) rx_buf; + + if (i2c_transfer(client->adapter, msgs, 2) < 2) return 0; - return (buffer[3] << 24) | (buffer[2] << 16) | - (buffer[1] << 8) | buffer[0]; + return (rx_buf[3] << 24) | (rx_buf[2] << 16) | (rx_buf[1] << 8) | + rx_buf[0]; } int cx25840_and_or(struct i2c_client *client, u16 addr, unsigned and_mask, -- 2.11.0