Re: [PATCHv2 2/2] hwrng: optee: fix wait use case

On Thu, 23 Jul 2020 at 14:16, Jorge Ramirez-Ortiz jorge@foundries.io wrote:

The current code waits for data to be available before attempting a second read. However the second read would not be executed as the while loop exits.

This fix does not wait if all data has been read and reads a second time if only partial data was retrieved on the first read.

This fix also does not attempt to read if not data is requested.

I am not sure how this is possible, can you elaborate?

Signed-off-by: Jorge Ramirez-Ortiz jorge@foundries.io

v2: tidy up the while loop to avoid reading when no data is requested

drivers/char/hw_random/optee-rng.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/char/hw_random/optee-rng.c b/drivers/char/hw_random/optee-rng.c index 5bc4700c4dae..a99d82949981 100644 --- a/drivers/char/hw_random/optee-rng.c +++ b/drivers/char/hw_random/optee-rng.c @@ -122,14 +122,14 @@ static int optee_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait) if (max > MAX_ENTROPY_REQ_SZ) max = MAX_ENTROPY_REQ_SZ;

•   while (read == 0) {
  

•   while (read < max) {
            rng_size = get_optee_rng_data(pvt_data, data, (max - read));
  
            data += rng_size;
            read += rng_size;
  
            if (wait && pvt_data->data_rate) {
  

•                   if (timeout-- == 0)
  

•                   if ((timeout-- == 0) || (read == max))
  

If read == max, would there be any sleep?

-Sumit

                            return read;
                    msleep((1000 * (max - read)) / pvt_data->data_rate);
            } else {

-- 2.17.1