linux-pci.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: "Sean O. Stalley" <sean.stalley@intel.com>
To: bhelgaas@google.com, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org
Cc: "Sean O. Stalley" <sean.stalley@intel.com>
Subject: [PATCH] Read ID & Pointer from PCI Capabilities List in 1 call
Date: Thu,  2 Apr 2015 14:10:19 -0700	[thread overview]
Message-ID: <1428009019-19563-1-git-send-email-sean.stalley@intel.com> (raw)

Reading both fields at the same time lets us parse the
list with half the number of configspace reads.

Signed-off-by: Sean O. Stalley <sean.stalley@intel.com>
---
 drivers/pci/pci.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 5e3c8e9..db7f3d6 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -145,19 +145,22 @@ static int __pci_find_next_cap_ttl(struct pci_bus *bus, unsigned int devfn,
 				   u8 pos, int cap, int *ttl)
 {
 	u8 id;
+	u16 ent;
+
+	pci_bus_read_config_byte(bus, devfn, pos, &pos);
 
 	while ((*ttl)--) {
-		pci_bus_read_config_byte(bus, devfn, pos, &pos);
 		if (pos < 0x40)
 			break;
 		pos &= ~3;
-		pci_bus_read_config_byte(bus, devfn, pos + PCI_CAP_LIST_ID,
-					 &id);
+		pci_bus_read_config_word(bus, devfn, pos, &ent);
+
+		id = ent & 0xff;
 		if (id == 0xff)
 			break;
 		if (id == cap)
 			return pos;
-		pos += PCI_CAP_LIST_NEXT;
+		pos = (ent >> 8);
 	}
 	return 0;
 }
-- 
1.9.1


             reply	other threads:[~2015-04-02 21:11 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-02 21:10 Sean O. Stalley [this message]
2015-04-09 22:12 ` [PATCH] Read ID & Pointer from PCI Capabilities List in 1 call Bjorn Helgaas

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=1428009019-19563-1-git-send-email-sean.stalley@intel.com \
    --to=sean.stalley@intel.com \
    --cc=bhelgaas@google.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pci@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;
as well as URLs for NNTP newsgroup(s).