From: Jiang Liu <jiang.liu@huawei.com>
To: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jiang Liu <liuj97@gmail.com>, Don Dutile <ddutile@redhat.com>,
Yinghai Lu <yinghai@kernel.org>,
Taku Izumi <izumi.taku@jp.fujitsu.com>,
"Rafael J . Wysocki" <rjw@sisk.pl>,
Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>,
Yijing Wang <wangyijing@huawei.com>,
Keping Chen <chenkeping@huawei.com>,
<linux-kernel@vger.kernel.org>, <linux-pci@vger.kernel.org>
Subject: Re: [RFC PATCH 06/14] PCI: use PCIe cap access functions to simplify PCI core implementation
Date: Wed, 11 Jul 2012 10:49:36 +0800 [thread overview]
Message-ID: <4FFCE9C0.3050705@huawei.com> (raw)
In-Reply-To: <CAErSpo5bx8+tdx5NFUuJurYRVDA42h2Bbrn0EdBJBF=J-8Muqg@mail.gmail.com>
On 2012-7-11 2:35, Bjorn Helgaas wrote:
>> @@ -2042,7 +1994,6 @@ void pci_free_cap_save_buffers(struct pci_dev *dev)
>> */
>> void pci_enable_ari(struct pci_dev *dev)
>> {
>> - int pos;
>> u32 cap;
>> u16 ctrl;
>> struct pci_dev *bridge;
>> @@ -2050,8 +2001,7 @@ void pci_enable_ari(struct pci_dev *dev)
>> if (pcie_ari_disabled || !pci_is_pcie(dev) || dev->devfn)
>> return;
>>
>> - pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI);
>> - if (!pos)
>> + if (pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI))
>
> What's going on here? This looks wrong, and unrelated to the rest of the patch.
Yeah, it's a bug. My original idea is to get rid of "int pos", and it should be
if (!pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI))
>
>> return;
>>
>> bridge = dev->bus->self;
>> @@ -2059,17 +2009,14 @@ void pci_enable_ari(struct pci_dev *dev)
>> return;
>>
>> /* ARI is a PCIe cap v2 feature */
>
> If we're doing this right, we should be able to remove this comment
> (and similar ones below).
Will remove them.
>
>> - pos = pci_pcie_cap2(bridge);
>> - if (!pos)
>> + if (pci_pcie_cap_read_dword(bridge, PCI_EXP_DEVCAP2, &cap) ||
>> + !(cap & PCI_EXP_DEVCAP2_ARI))
>
> I don't think there's any point in checking every return from
> pci_pcie_cap_read_dword(). We've already checked pci_is_pcie() above,
> and checking here just clutters the code. In cases like this, my
> opinion is that clean code leads to fewer bugs, and that benefit
> outweighs whatever technical "every return must be checked" benefit
> there might be.
Good point!
>> @@ -2223,17 +2152,14 @@ EXPORT_SYMBOL(pci_disable_obff);
>> */
>> static bool pci_ltr_supported(struct pci_dev *dev)
>> {
>> - int pos;
>> u32 cap;
>>
>> /* LTR is a PCIe cap v2 feature */
>> - pos = pci_pcie_cap2(dev);
>> - if (!pos)
>> + if (pci_pcie_cap_read_dword(dev, PCI_EXP_DEVCAP2, &cap) ||
>> + !(cap & PCI_EXP_DEVCAP2_LTR))
>> return false;
>
> How about if you restructure this to avoid the double negatives? E.g.,
>
> pci_pcie_cap_read_dword(dev, PCI_EXP_DEVCAP2, &cap);
> if (cap & PCI_EXP_DEVCAP2_LTR)
> return true;
>
> return false;
>
Good point.
Thanks!
Gerry
next prev parent reply other threads:[~2012-07-11 2:53 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-04 7:44 [Resend with Ack][PATCH v1] PCI: allow acpiphp to handle PCIe ports without native PCIe hotplug capability Jiang Liu
2012-06-04 8:23 ` Kenji Kaneshige
2012-07-03 4:16 ` Bjorn Helgaas
2012-07-03 15:59 ` Bjorn Helgaas
2012-07-03 19:50 ` Don Dutile
2012-07-04 18:07 ` Bjorn Helgaas
2012-07-09 10:05 ` Jiang Liu
2012-07-09 17:05 ` Bjorn Helgaas
2012-07-04 2:52 ` Jiang Liu
2012-07-10 15:54 ` [RFC PATCH 00/14] improve PCIe capabilities registers handling Jiang Liu
2012-07-10 18:44 ` Bjorn Helgaas
2012-07-10 15:54 ` [RFC PATCH 01/14] PCI: add pcie_flags into struct pci_dev to cache PCIe capabilities register Jiang Liu
2012-07-11 9:01 ` Taku Izumi
2012-07-11 14:27 ` Jiang Liu
2012-07-10 15:54 ` [RFC PATCH 02/14] PCI: introduce pci_pcie_type(dev) to replace pci_dev->pcie_type Jiang Liu
2012-07-10 15:54 ` [RFC PATCH 03/14] PCI: remove unused field pcie_type from struct pci_dev Jiang Liu
2012-07-10 15:54 ` [RFC PATCH 04/14] PCI: refine and move pcie_cap_has_*() macros to include/linux/pci.h Jiang Liu
2012-07-10 18:49 ` Bjorn Helgaas
2012-07-10 15:54 ` [RFC PATCH 05/14] PCI: add access functions for PCIe capabilities to hide PCIe spec differences Jiang Liu
2012-07-10 18:35 ` Bjorn Helgaas
2012-07-11 3:07 ` Jiang Liu
2012-07-11 3:40 ` Bjorn Helgaas
2012-07-11 6:40 ` Jiang Liu
2012-07-11 17:52 ` Bjorn Helgaas
2012-07-12 2:56 ` Jiang Liu
2012-07-12 20:49 ` Bjorn Helgaas
2012-07-15 16:47 ` Jiang Liu
2012-07-16 17:29 ` Bjorn Helgaas
2012-07-16 18:57 ` Don Dutile
2012-07-17 0:09 ` Jiang Liu
2012-07-17 0:14 ` Bjorn Helgaas
2012-07-10 15:54 ` [RFC PATCH 06/14] PCI: use PCIe cap access functions to simplify PCI core implementation Jiang Liu
2012-07-10 18:35 ` Bjorn Helgaas
2012-07-11 2:49 ` Jiang Liu [this message]
2012-07-10 15:54 ` [RFC PATCH 07/14] hotplug/PCI: use PCIe cap access functions to simplify implementation Jiang Liu
2012-07-10 18:35 ` Bjorn Helgaas
2012-07-10 15:54 ` [RFC PATCH 08/14] portdrv/PCI: " Jiang Liu
2012-07-10 15:54 ` [RFC PATCH 09/14] pciehp/PCI: " Jiang Liu
2012-07-10 15:54 ` [RFC PATCH 10/14] PME/PCI: " Jiang Liu
2012-07-10 15:54 ` [RFC PATCH 11/14] AER/PCI: " Jiang Liu
2012-07-10 15:54 ` [RFC PATCH 12/14] ASPM/PCI: " Jiang Liu
2012-07-10 15:54 ` [RFC PATCH 13/14] r8169/PCI: " Jiang Liu
2012-07-10 15:54 ` [RFC PATCH 14/14] qib/PCI: " Jiang Liu
2012-08-15 19:12 ` [Resend with Ack][PATCH v1] PCI: allow acpiphp to handle PCIe ports without native PCIe hotplug capability Bjorn Helgaas
2012-08-16 15:15 ` Jiang Liu
2012-08-22 15:16 ` [PATCH v2] PCI: allow acpiphp to handle PCIe ports w/o " Jiang Liu
2012-09-24 22:10 ` Bjorn Helgaas
2012-09-25 15:16 ` Jiang Liu
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