Re: [PATCHv2] usb: typec: tps6598x: handle block writes separately with plain-I2C adapters

From: Nikolaus Voss
Date: Wed Feb 20 2019 - 10:18:13 EST


On Wed, 20 Feb 2019, Guenter Roeck wrote:
On 2/20/19 4:57 AM, Nikolaus Voss wrote:
Commit 1a2f474d328f handles block _reads_ separately with plain-I2C
adapters, but the problem described with regmap-i2c not handling
SMBus block transfers (i.e. read and writes) correctly also exists
with writes.

As workaround, this patch adds a block write function the same way
1a2f474d328f adds a block read function.

Fixes: 1a2f474d328f ("usb: typec: tps6598x: handle block reads separately with plain-I2C adapters")
Fixes: 0a4c005bd171 ("usb: typec: driver for TI TPS6598x USB Power Delivery controllers")
Signed-off-by: Nikolaus Voss <nikolaus.voss@xxxxxxxxxxxxxxxxxxxxx>
---
v2: fix tps6598x_exec_cmd also
---
drivers/usb/typec/tps6598x.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/typec/tps6598x.c b/drivers/usb/typec/tps6598x.c
index c84c8c189e90..c54b73fb2a2f 100644
--- a/drivers/usb/typec/tps6598x.c
+++ b/drivers/usb/typec/tps6598x.c
@@ -110,6 +110,20 @@ tps6598x_block_read(struct tps6598x *tps, u8 reg, void *val, size_t len)
return 0;
}
+static int tps6598x_block_write(struct tps6598x *tps, u8 reg,
+ void *val, size_t len)
+{
+ u8 data[len + 1];
+

You should use TPS_MAX_LEN + 1 here to avoid the variable length array.
See upstream commit 0bb95f80a38f8 ("Makefile: Globally enable VLA warning")
and 8d361fa2c29dc ("usb: typec: tps6598x: Remove VLA usage"). Not sure if
the WARN_ON introduced by 8d361fa2c29dc is really needed; I dislike
unnecessary runtime checks.

Thanks for the pointer, I fixed this...

Nikolaus