From a841178445bb72a3d566b4e6ab9d19e9b002eb47 Mon Sep 17 00:00:00 2001 From: Javier Martinez Canillas Date: Tue, 9 Jun 2015 13:04:42 +0200 Subject: mfd: cros_ec: Use a zero-length array for command data Commit 1b84f2a4cd4a ("mfd: cros_ec: Use fixed size arrays to transfer data with the EC") modified the struct cros_ec_command fields to not use pointers for the input and output buffers and use fixed length arrays instead. This change was made because the cros_ec ioctl API uses that struct cros_ec_command to allow user-space to send commands to the EC and to get data from the EC. So using pointers made the API not 64-bit safe. Unfortunately this approach was not flexible enough for all the use-cases since there may be a need to send larger commands on newer versions of the EC command protocol. So to avoid to choose a constant length that it may be too big for most commands and thus wasting memory and CPU cycles on copy from and to user-space or having a size that is too small for some big commands, use a zero-length array that is both 64-bit safe and flexible. The same buffer is used for both output and input data so the maximum of these values should be used to allocate it. Suggested-by: Gwendal Grignou Signed-off-by: Javier Martinez Canillas Tested-by: Heiko Stuebner Acked-by: Lee Jones Acked-by: Olof Johansson Signed-off-by: Lee Jones --- include/linux/mfd/cros_ec.h | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'include/linux/mfd/cros_ec.h') diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h index 14cf522123dd..7eee38abd02a 100644 --- a/include/linux/mfd/cros_ec.h +++ b/include/linux/mfd/cros_ec.h @@ -42,8 +42,7 @@ enum { * @outsize: Outgoing length in bytes * @insize: Max number of bytes to accept from EC * @result: EC's response to the command (separate from communication failure) - * @outdata: Outgoing data to EC - * @indata: Where to put the incoming data from EC + * @data: Where to put the incoming data from EC and outgoing data to EC */ struct cros_ec_command { uint32_t version; @@ -51,8 +50,7 @@ struct cros_ec_command { uint32_t outsize; uint32_t insize; uint32_t result; - uint8_t outdata[EC_PROTO2_MAX_PARAM_SIZE]; - uint8_t indata[EC_PROTO2_MAX_PARAM_SIZE]; + uint8_t data[0]; }; /** -- cgit v1.2.3