From: Sascha Hauer <s.hauer@pengutronix.de>
To: Ahmad Fatoum <a.fatoum@pengutronix.de>
Cc: Tomas Marek <tomas.marek@elrest.cz>, barebox@lists.infradead.org
Subject: Re: [PATCH 5/6] i2c: efi: avoid 64-bit division
Date: Mon, 19 Aug 2024 08:16:13 +0200 [thread overview]
Message-ID: <ZsLjLZLzHfQfAWdB@pengutronix.de> (raw)
In-Reply-To: <f8931b23-768b-429e-a634-b28494fb95fa@pengutronix.de>
On Thu, Aug 15, 2024 at 08:57:18AM +0200, Ahmad Fatoum wrote:
> Hello Tomas,
>
> On 15.08.24 07:53, Tomas Marek wrote:
> > Hello Ahmad,
> >
> > Thanks for maintenance of the Barebox EFI.
> >
> > On Wed, Aug 14, 2024 at 11:24:23AM +0200, Ahmad Fatoum wrote:
> >> I2C message length is 16 bit, so doing a 64-bit division is overkill.
> >> Let's remove the cast and just rely on the usual integer promotion
> >> to 32-bit.
> >>
> >> Cc: Tomas Marek <tomas.marek@elrest.cz>
> >> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> >> ---
> >> drivers/i2c/busses/i2c-efi.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/i2c/busses/i2c-efi.c b/drivers/i2c/busses/i2c-efi.c
> >> index 5f6cc0eed28e..a666a28fab51 100644
> >> --- a/drivers/i2c/busses/i2c-efi.c
> >> +++ b/drivers/i2c/busses/i2c-efi.c
> >> @@ -114,7 +114,7 @@ static unsigned int efi_i2c_msg_op_cnt(const struct efi_i2c_priv *i2c_priv,
> >>
> >> max_len = efi_i2c_max_len(i2c_priv, msg);
> >>
> >> - return ((u64)msg->len + max_len - 1) / max_len;
> >> + return (msg->len + max_len - 1) / max_len;
> >
> > The issue here is that max_len, which represents the MaximumReceiveBytes
> > or MaximumTransmitBytes in EFI I2C capabilities, is 32-bit. In some EFI
> > implementations (including the one I use), the EFI I2C MaximumReceiveBytes
> > and MaximumTransmitBytes are set to the maximum value (0xFFFFFFFF). This
> > causes msg->len + max_len - 1 to overflow, leading to an incorrect number
> > of returned operations. To address this, the msg->len is extended to 64 bits.
>
> Thanks for the info. See the patch I just Cc'd you on.
>
> @Sascha, can you drop this one patch again?
Ok, reverted it.
Sascha
--
Pengutronix e.K. | |
Steuerwalder Str. 21 | http://www.pengutronix.de/ |
31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
next prev parent reply other threads:[~2024-08-19 6:17 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-14 9:24 [PATCH 1/6] common: pe: fix use of undefined macro for ARMv7 Ahmad Fatoum
2024-08-14 9:24 ` [PATCH 2/6] efi: fs: fix determination of read-only files Ahmad Fatoum
2024-08-14 9:24 ` [PATCH 3/6] filetype: fix else clause indentation Ahmad Fatoum
2024-08-14 9:24 ` [PATCH 4/6] acpi: fix compilation for 32-bit Ahmad Fatoum
2024-08-14 9:24 ` [PATCH 5/6] i2c: efi: avoid 64-bit division Ahmad Fatoum
2024-08-15 5:53 ` Tomas Marek
2024-08-15 6:57 ` Ahmad Fatoum
2024-08-19 6:16 ` Sascha Hauer [this message]
2024-08-14 9:24 ` [PATCH 6/6] net: fsl_enetc: fix compilation for 32-bit Ahmad Fatoum
2024-08-14 11:08 ` [PATCH 1/6] common: pe: fix use of undefined macro for ARMv7 Sascha Hauer
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ZsLjLZLzHfQfAWdB@pengutronix.de \
--to=s.hauer@pengutronix.de \
--cc=a.fatoum@pengutronix.de \
--cc=barebox@lists.infradead.org \
--cc=tomas.marek@elrest.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox