mirror of https://lore.kernel.org/lkml/
 help / color / mirror / Atom feed
From: Dan Carpenter <dan.carpenter@oracle.com>
To: Len Brown <lenb@kernel.org>
Cc: linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
	kernel-janitors@vger.kernel.org
Subject: [patch] acpi throttling: fix endian bug in acpi_read_throttling_status()
Date: Wed, 7 Mar 2012 14:57:36 +0300	[thread overview]
Message-ID: <20120307115736.GB13204@elgon.mountain> (raw)

Using a u64 here creates an endian bug.  We store a u32 number in the
top byte which is a larger number than intended on big endian systems.
There is no reason to use a 64 bit data type here, I guess it was just
an oversight.

I removed the initialization to zero as well.  It's needed with a u64
but with a u32, the variable gets initialized properly inside the call
to acpi_os_read_port().

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/drivers/acpi/processor_throttling.c b/drivers/acpi/processor_throttling.c
index 605a295..1d02b7b 100644
--- a/drivers/acpi/processor_throttling.c
+++ b/drivers/acpi/processor_throttling.c
@@ -769,7 +769,7 @@ static int acpi_read_throttling_status(struct acpi_processor *pr,
 					u64 *value)
 {
 	u32 bit_width, bit_offset;
-	u64 ptc_value;
+	u32 ptc_value;
 	u64 ptc_mask;
 	struct acpi_processor_throttling *throttling;
 	int ret = -1;
@@ -777,12 +777,11 @@ static int acpi_read_throttling_status(struct acpi_processor *pr,
 	throttling = &pr->throttling;
 	switch (throttling->status_register.space_id) {
 	case ACPI_ADR_SPACE_SYSTEM_IO:
-		ptc_value = 0;
 		bit_width = throttling->status_register.bit_width;
 		bit_offset = throttling->status_register.bit_offset;
 
 		acpi_os_read_port((acpi_io_address) throttling->status_register.
-				  address, (u32 *) &ptc_value,
+				  address, &ptc_value,
 				  (u32) (bit_width + bit_offset));
 		ptc_mask = (1 << bit_width) - 1;
 		*value = (u64) ((ptc_value >> bit_offset) & ptc_mask);

                 reply	other threads:[~2012-03-07 11:57 UTC|newest]

Thread overview: [no followups] expand[flat|nested]  mbox.gz  Atom feed

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=20120307115736.GB13204@elgon.mountain \
    --to=dan.carpenter@oracle.com \
    --cc=kernel-janitors@vger.kernel.org \
    --cc=lenb@kernel.org \
    --cc=linux-acpi@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    /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

all inboxes | Powered by JetHome®