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From: Sumit Garg <sumit.garg@linaro.org>
To: Jorge Ramirez-Ortiz <jorge@foundries.io>
Cc: Matt Mackall <mpm@selenic.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Jens Wiklander <jens.wiklander@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>,
	ricardo@foundries.io, Michael Scott <mike@foundries.io>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	op-tee@lists.trustedfirmware.org,
	"open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
	<linux-crypto@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCHv2 2/2] hwrng: optee: fix wait use case
Date: Fri, 24 Jul 2020 18:52:07 +0530
Message-ID: <CAFA6WYPQ3GGYostoHU=6qg4c_LqoqOZVbZ8gbQbGkNfyGydQjQ@mail.gmail.com> (raw)
In-Reply-To: <20200723084622.31134-2-jorge@foundries.io>

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
>

  reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-23  8:46 [PATCHv2 1/2] hwrng: optee: handle unlimited data rates Jorge Ramirez-Ortiz
2020-07-23  8:46 ` [PATCHv2 2/2] hwrng: optee: fix wait use case Jorge Ramirez-Ortiz
2020-07-24 13:22   ` Sumit Garg [this message]
2020-07-24 14:23     ` Jorge Ramirez-Ortiz, Foundries
2020-07-28 10:05       ` Jorge Ramirez-Ortiz, Foundries
2020-08-05 13:49       ` Sumit Garg
2020-08-05 20:38         ` Jorge Ramirez-Ortiz, Foundries
2020-08-06  6:11           ` Sumit Garg
2020-08-06  6:30             ` Jorge Ramirez-Ortiz, Foundries
2020-08-06  6:57               ` Sumit Garg
2020-08-06  8:14                 ` Jorge Ramirez-Ortiz, Foundries
2020-08-06  9:15                   ` Sumit Garg
2020-08-05 13:34   ` Jorge Ramirez-Ortiz, Foundries
2020-07-24 13:24 ` [PATCHv2 1/2] hwrng: optee: handle unlimited data rates Sumit Garg

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