From: Wolfram Sang <wsa@the-dreams.de>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Wolfram Sang" <wsa+renesas@sang-engineering.com>,
"Linux MMC List" <linux-mmc@vger.kernel.org>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
"Yoshihiro Shimoda" <yoshihiro.shimoda.uh@renesas.com>,
"Masahiro Yamada" <yamada.masahiro@socionext.com>,
"Niklas Söderlund" <niklas.soderlund@ragnatech.se>
Subject: Re: [RFC PATCH 2/2] mmc: renesas_sdhi: prevent overflow for max_req_size
Date: Fri, 15 Mar 2019 12:01:31 +0100 [thread overview]
Message-ID: <20190315110130.GA2148@kunai> (raw)
In-Reply-To: <CAMuHMdUmNSk3n1EEaYQpXV-Pwa3d9O8UDARx+zF5c_BYqrR5rg@mail.gmail.com>
> My worry here is that if several drivers would do
>
> .max_blk_count = UINT_MAX / DRIVER_SPECIFIC_MAX_BLK_SIZE,
>
> Those drivers can safely calculate "max_blk_size * max_blk_count".
> People may start assuming this is always safe. while the core cannot do
> "GLOBAL_MAX_BLK_SIZE * max_blk_count" using 32-bit arithmetic, as the
> latter may still overflow, depending on the driver.
The core will not do this calculation. This is why the variable
max_req_size exists. It will just use this variable which shall be setup
by the driver which may impose other restrictions, too (And there can't
be a GLOBAL_MAX_BLK_SIZE anyhow)
So, when calculating max_req_size, it is the duty of the driver not to
overflow. Or?
next prev parent reply other threads:[~2019-03-15 11:01 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-14 22:31 [RFC PATCH 0/2] mmc: renesas_sdhi: prevent overflow for max_req_size Wolfram Sang
2019-03-14 22:31 ` [RFC PATCH 1/2] mmc: tmio: introduce macro for max block size Wolfram Sang
2019-03-25 13:26 ` Ulf Hansson
2019-03-14 22:31 ` [RFC PATCH 2/2] mmc: renesas_sdhi: prevent overflow for max_req_size Wolfram Sang
2019-03-15 7:46 ` Geert Uytterhoeven
2019-03-15 8:29 ` Wolfram Sang
2019-03-15 8:49 ` Geert Uytterhoeven
2019-03-15 9:28 ` Wolfram Sang
2019-03-15 9:35 ` Geert Uytterhoeven
2019-03-15 9:39 ` Wolfram Sang
2019-03-15 9:46 ` Geert Uytterhoeven
2019-03-15 11:01 ` Wolfram Sang [this message]
2019-03-25 13:26 ` Ulf Hansson
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