From: Rob Herring <robh@kernel.org> To: Naveen Naidu <naveennaidu479@gmail.com> Cc: Bjorn Helgaas <bhelgaas@google.com>, linux-kernel-mentees@lists.linuxfoundation.org, PCI <linux-pci@vger.kernel.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org> Subject: Re: [PATCH 02/22] PCI: Unify PCI error response checking Date: Tue, 12 Oct 2021 13:02:39 -0500 [thread overview] Message-ID: <CAL_JsqKYP+6Bzm5hvcVbAz5R3+omREDJoOspJ4eTBeMwBSfkfw@mail.gmail.com> (raw) In-Reply-To: <20211012162054.rxx7aubwdvhl2eqj@theprophet> On Tue, Oct 12, 2021 at 11:21 AM Naveen Naidu <naveennaidu479@gmail.com> wrote: > > On 11/10, Rob Herring wrote: > > On Mon, Oct 11, 2021 at 11:08:32PM +0530, Naveen Naidu wrote: > > > An MMIO read from a PCI device that doesn't exist or doesn't respond > > > causes a PCI error. There's no real data to return to satisfy the > > > CPU read, so most hardware fabricates ~0 data. > > > > > > Use SET_PCI_ERROR_RESPONSE() to set the error response and > > > RESPONSE_IS_PCI_ERROR() to check the error response during hardware > > > read. > > > > > > These definitions make error checks consistent and easier to find. > > > > > > Signed-off-by: Naveen Naidu <naveennaidu479@gmail.com> > > > --- > > > drivers/pci/access.c | 22 +++++++++++----------- > > > 1 file changed, 11 insertions(+), 11 deletions(-) > > > > > > diff --git a/drivers/pci/access.c b/drivers/pci/access.c > > > index 46935695cfb9..e1954bbbd137 100644 > > > --- a/drivers/pci/access.c > > > +++ b/drivers/pci/access.c > > > @@ -81,7 +81,7 @@ int pci_generic_config_read(struct pci_bus *bus, unsigned int devfn, > > > > > > addr = bus->ops->map_bus(bus, devfn, where); > > > if (!addr) { > > > - *val = ~0; > > > + SET_PCI_ERROR_RESPONSE(val); > > > > This to me doesn't look like kernel style. I'd rather see a define > > replace just '~0', but I defer to Bjorn. > > > > Apologies, if this is a lame question. Why is the macro > SET_PCI_ERROR_RESPONSE not a kernel style. I ask this so that I do not > end up making the same mistake again. Generally, we don't do macros if a static inline function will work because you get more type checking with a function. There's exceptions like struct initializers which need to work in declarations. Second, I think the above obfuscates the code. I know exactly what the original line is doing to val. With SET_PCI_ERROR_RESPONSE(), I have to go look and it hasn't saved us any LOC to make the caller more readable. The downside of the original way, is I don't know why we set val to ~0, but just a define would tell me that. > Bjorn, did initally make a patch with only replacing '~0' but then > Andrew suggested in the patch [1] that we should use the macro. > > [1]: > https://lore.kernel.org/linux-pci/20190823104415.GC14582@e119886-lin.cambridge.arm.com/ > [Adding Andrew in the CC for this] He's no longer at Arm nor active upstream. > Apologies, I should have added this link in the cover letter but I > completely forgot about it. > > That's why I decided to go with the macro. If that is not the right > approach please let me know and I can fix it up. > > > > return PCIBIOS_DEVICE_NOT_FOUND; > > > > Neither does this using custom error codes rather than standard Linux > > errno. I point this out as I that's were I'd start with the config > > accessors. Though there are lots of occurrences so we'd need a way to do > > this in manageable steps. > > > > I am sorry, but I do not have any answer for this. I really do not know > why we return custom error codes instead of standard Linux errno. Maybe > someone else can pitch in on this. I don't either. My guess is either just too many places to fix or somehow it trickles up to userspace (but probably not since the error codes aren't in a uapi header). > > Can't we make PCI_OP_READ and PCI_USER_READ_CONFIG set the data value > > and delete the drivers all doing this? Then we have 2 copies (in source) > > rather than the many this series modifies. Though I'm not sure if there > > are other cases of calling pci_bus.ops.read() which expect to get ~0. > > > > This seems like a really good idea :) But again, I am not entirely sure > if doing so would give us any unexpected behaviour. I'll wait for some > one to reply to this and if people agree to it, I would be glad to make > the changes to PCI_OP_READ and PCI_USER_READ_CONFIG and send a new > patch. I'm expecting Bjorn to chime in. Rob
WARNING: multiple messages have this Message-ID (diff)
From: Rob Herring <robh@kernel.org> To: Naveen Naidu <naveennaidu479@gmail.com> Cc: Bjorn Helgaas <bhelgaas@google.com>, PCI <linux-pci@vger.kernel.org>, linux-kernel-mentees@lists.linuxfoundation.org, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org> Subject: Re: [PATCH 02/22] PCI: Unify PCI error response checking Date: Tue, 12 Oct 2021 13:02:39 -0500 [thread overview] Message-ID: <CAL_JsqKYP+6Bzm5hvcVbAz5R3+omREDJoOspJ4eTBeMwBSfkfw@mail.gmail.com> (raw) In-Reply-To: <20211012162054.rxx7aubwdvhl2eqj@theprophet> On Tue, Oct 12, 2021 at 11:21 AM Naveen Naidu <naveennaidu479@gmail.com> wrote: > > On 11/10, Rob Herring wrote: > > On Mon, Oct 11, 2021 at 11:08:32PM +0530, Naveen Naidu wrote: > > > An MMIO read from a PCI device that doesn't exist or doesn't respond > > > causes a PCI error. There's no real data to return to satisfy the > > > CPU read, so most hardware fabricates ~0 data. > > > > > > Use SET_PCI_ERROR_RESPONSE() to set the error response and > > > RESPONSE_IS_PCI_ERROR() to check the error response during hardware > > > read. > > > > > > These definitions make error checks consistent and easier to find. > > > > > > Signed-off-by: Naveen Naidu <naveennaidu479@gmail.com> > > > --- > > > drivers/pci/access.c | 22 +++++++++++----------- > > > 1 file changed, 11 insertions(+), 11 deletions(-) > > > > > > diff --git a/drivers/pci/access.c b/drivers/pci/access.c > > > index 46935695cfb9..e1954bbbd137 100644 > > > --- a/drivers/pci/access.c > > > +++ b/drivers/pci/access.c > > > @@ -81,7 +81,7 @@ int pci_generic_config_read(struct pci_bus *bus, unsigned int devfn, > > > > > > addr = bus->ops->map_bus(bus, devfn, where); > > > if (!addr) { > > > - *val = ~0; > > > + SET_PCI_ERROR_RESPONSE(val); > > > > This to me doesn't look like kernel style. I'd rather see a define > > replace just '~0', but I defer to Bjorn. > > > > Apologies, if this is a lame question. Why is the macro > SET_PCI_ERROR_RESPONSE not a kernel style. I ask this so that I do not > end up making the same mistake again. Generally, we don't do macros if a static inline function will work because you get more type checking with a function. There's exceptions like struct initializers which need to work in declarations. Second, I think the above obfuscates the code. I know exactly what the original line is doing to val. With SET_PCI_ERROR_RESPONSE(), I have to go look and it hasn't saved us any LOC to make the caller more readable. The downside of the original way, is I don't know why we set val to ~0, but just a define would tell me that. > Bjorn, did initally make a patch with only replacing '~0' but then > Andrew suggested in the patch [1] that we should use the macro. > > [1]: > https://lore.kernel.org/linux-pci/20190823104415.GC14582@e119886-lin.cambridge.arm.com/ > [Adding Andrew in the CC for this] He's no longer at Arm nor active upstream. > Apologies, I should have added this link in the cover letter but I > completely forgot about it. > > That's why I decided to go with the macro. If that is not the right > approach please let me know and I can fix it up. > > > > return PCIBIOS_DEVICE_NOT_FOUND; > > > > Neither does this using custom error codes rather than standard Linux > > errno. I point this out as I that's were I'd start with the config > > accessors. Though there are lots of occurrences so we'd need a way to do > > this in manageable steps. > > > > I am sorry, but I do not have any answer for this. I really do not know > why we return custom error codes instead of standard Linux errno. Maybe > someone else can pitch in on this. I don't either. My guess is either just too many places to fix or somehow it trickles up to userspace (but probably not since the error codes aren't in a uapi header). > > Can't we make PCI_OP_READ and PCI_USER_READ_CONFIG set the data value > > and delete the drivers all doing this? Then we have 2 copies (in source) > > rather than the many this series modifies. Though I'm not sure if there > > are other cases of calling pci_bus.ops.read() which expect to get ~0. > > > > This seems like a really good idea :) But again, I am not entirely sure > if doing so would give us any unexpected behaviour. I'll wait for some > one to reply to this and if people agree to it, I would be glad to make > the changes to PCI_OP_READ and PCI_USER_READ_CONFIG and send a new > patch. I'm expecting Bjorn to chime in. Rob _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
next prev parent reply other threads:[~2021-10-12 18:03 UTC|newest] Thread overview: 117+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-10-11 17:35 [PATCH 00/22] PCI: Unify PCI error response checking Naveen Naidu 2021-10-11 17:35 ` Naveen Naidu 2021-10-11 17:35 ` Naveen Naidu 2021-10-11 17:35 ` Naveen Naidu 2021-10-11 17:35 ` Naveen Naidu 2021-10-11 17:35 ` Naveen Naidu 2021-10-11 17:37 ` [PATCH 01/22] PCI: Add PCI_ERROR_RESPONSE and it's related defintions Naveen Naidu 2021-10-11 17:37 ` Naveen Naidu 2021-10-11 17:37 ` Naveen Naidu 2021-10-11 17:37 ` Naveen Naidu 2021-10-11 17:37 ` Naveen Naidu 2021-10-11 17:37 ` Naveen Naidu 2021-10-11 17:38 ` [PATCH 02/22] PCI: Unify PCI error response checking Naveen Naidu 2021-10-11 17:38 ` Naveen Naidu 2021-10-11 22:05 ` Rob Herring 2021-10-11 22:05 ` Rob Herring 2021-10-12 16:21 ` Naveen Naidu 2021-10-12 16:21 ` Naveen Naidu 2021-10-12 18:02 ` Rob Herring [this message] 2021-10-12 18:02 ` Rob Herring 2021-10-12 22:52 ` Pali Rohár 2021-10-12 22:52 ` Pali Rohár 2021-10-13 2:43 ` Bjorn Helgaas 2021-10-13 2:43 ` Bjorn Helgaas 2021-10-13 13:06 ` Rob Herring 2021-10-13 13:06 ` Rob Herring 2021-10-13 17:16 ` Naveen Naidu 2021-10-13 17:16 ` Naveen Naidu 2021-10-13 17:54 ` Pali Rohár 2021-10-13 17:54 ` Pali Rohár 2021-10-13 18:48 ` Bjorn Helgaas 2021-10-13 18:48 ` Bjorn Helgaas 2021-10-13 21:47 ` Rob Herring 2021-10-13 21:47 ` Rob Herring 2021-10-13 22:03 ` Pali Rohár 2021-10-13 22:03 ` Pali Rohár 2021-10-13 22:12 ` Bjorn Helgaas 2021-10-13 22:12 ` Bjorn Helgaas 2021-10-11 17:45 ` [PATCH 03/22] PCI: thunder: Use SET_PCI_ERROR_RESPONSE() when device not found Naveen Naidu 2021-10-11 17:45 ` Naveen Naidu 2021-10-11 17:45 ` Naveen Naidu 2021-10-11 17:46 ` [PATCH 04/22] PCI: iproc: " Naveen Naidu 2021-10-11 17:46 ` Naveen Naidu 2021-10-11 17:46 ` Naveen Naidu 2021-10-11 17:51 ` [PATCH 05/22] PCI: mediatek: " Naveen Naidu 2021-10-11 17:51 ` Naveen Naidu 2021-10-11 17:51 ` Naveen Naidu 2021-10-11 17:51 ` Naveen Naidu 2021-10-11 17:52 ` [PATCH 06/22] PCI: exynos: " Naveen Naidu 2021-10-11 17:52 ` Naveen Naidu 2021-10-11 17:52 ` Naveen Naidu 2021-10-11 17:53 ` [PATCH 07/22] PCI: histb: " Naveen Naidu 2021-10-11 17:53 ` Naveen Naidu 2021-10-11 17:55 ` [PATCH 08/22] PCI: kirin: " Naveen Naidu 2021-10-11 17:55 ` Naveen Naidu 2021-10-11 17:56 ` [PATCH 09/22] PCI: aardvark: " Naveen Naidu 2021-10-11 17:56 ` Naveen Naidu 2021-10-11 17:56 ` Naveen Naidu 2021-10-11 18:08 ` Pali Rohár 2021-10-11 18:08 ` Pali Rohár 2021-10-11 18:08 ` Pali Rohár 2021-10-11 18:28 ` Naveen Naidu 2021-10-11 18:28 ` Naveen Naidu 2021-10-11 18:28 ` Naveen Naidu [not found] ` <20211011182526.kboaxqofdpd2jjrl@theprophet> 2021-10-11 18:41 ` Pali Rohár 2021-10-11 18:41 ` Pali Rohár 2021-10-11 18:41 ` Pali Rohár 2021-10-12 15:59 ` Naveen Naidu 2021-10-12 15:59 ` Naveen Naidu 2021-10-12 15:59 ` Naveen Naidu 2021-10-13 2:13 ` Bjorn Helgaas 2021-10-13 2:13 ` Bjorn Helgaas 2021-10-13 2:13 ` Bjorn Helgaas 2021-10-13 17:59 ` Pali Rohár 2021-10-13 17:59 ` Pali Rohár 2021-10-13 17:59 ` Pali Rohár 2021-10-11 18:00 ` [PATCH 10/22] PCI: mvebu: " Naveen Naidu 2021-10-11 18:00 ` Naveen Naidu 2021-10-11 18:00 ` Naveen Naidu 2021-10-11 18:00 ` [PATCH 11/22] PCI: altera: " Naveen Naidu 2021-10-11 18:00 ` Naveen Naidu 2021-10-11 18:02 ` [PATCH 12/22] PCI: rcar: " Naveen Naidu 2021-10-11 18:02 ` Naveen Naidu 2021-10-11 18:02 ` [PATCH 13/22] PCI: rockchip: " Naveen Naidu 2021-10-11 18:02 ` Naveen Naidu 2021-10-11 18:02 ` Naveen Naidu 2021-10-11 18:02 ` Naveen Naidu 2021-10-11 18:04 ` [PATCH 14/22] PCI/ERR: Use RESPONSE_IS_PCI_ERROR() to check read from hardware Naveen Naidu 2021-10-11 18:04 ` Naveen Naidu 2021-10-11 18:06 ` [PATCH 15/22] PCI: vmd: " Naveen Naidu 2021-10-11 18:06 ` Naveen Naidu 2021-10-14 18:04 ` Jonathan Derrick 2021-10-14 18:04 ` Jonathan Derrick 2021-10-11 18:07 ` [PATCH 16/22] PCI: pciehp: " Naveen Naidu 2021-10-11 18:07 ` Naveen Naidu 2021-10-11 19:47 ` Lukas Wunner 2021-10-11 19:47 ` Lukas Wunner 2021-10-12 16:05 ` Naveen Naidu 2021-10-12 16:05 ` Naveen Naidu 2021-10-12 23:12 ` Pali Rohár 2021-10-12 23:12 ` Pali Rohár 2021-10-13 12:20 ` Lukas Wunner 2021-10-13 12:20 ` Lukas Wunner 2021-10-11 18:08 ` [PATCH 17/22] PCI/DPC: " Naveen Naidu 2021-10-11 18:08 ` Naveen Naidu 2021-10-11 18:08 ` Naveen Naidu 2021-10-11 18:10 ` [PATCH 18/22] PCI/PME: " Naveen Naidu 2021-10-11 18:10 ` Naveen Naidu 2021-10-11 18:11 ` [PATCH 19/22] PCI: cpqphp: " Naveen Naidu 2021-10-11 18:11 ` Naveen Naidu 2021-10-11 18:11 ` [PATCH 20/22] PCI: keystone: Use PCI_ERROR_RESPONSE to specify hardware error Naveen Naidu 2021-10-11 18:11 ` Naveen Naidu 2021-10-11 18:12 ` [PATCH 21/22] PCI: hv: Use PCI_ERROR_RESPONSE to specify hardware read error Naveen Naidu 2021-10-11 18:12 ` Naveen Naidu 2021-10-11 18:13 ` [PATCH 22/22] PCI: xgene: Use PCI_ERROR_RESPONSE to specify hardware error Naveen Naidu 2021-10-11 18:13 ` Naveen Naidu 2021-10-11 18:13 ` Naveen Naidu
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