From: "Arnd Bergmann" <arnd@kernel•org>
To: "Bjorn Helgaas" <helgaas@kernel•org>,
"Gerd Bayer" <gbayer@linux•ibm.com>
Cc: "Hans Zhang" <18255117159@163•com>,
bhelgaas@google•com, "Alexander Gordeev" <agordeev@linux•ibm.com>,
"Christian Borntraeger" <borntraeger@linux•ibm.com>,
"Ilpo Järvinen" <ilpo.jarvinen@linux•intel.com>,
jingoohan1@gmail•com,
"Krzysztof Wilczyński" <kwilczynski@kernel•org>,
linux-kernel@vger•kernel.org, linux-s390@vger•kernel.org,
linux-next <linux-next@vger•kernel.org>,
linux-pci@vger•kernel.org,
"Lorenzo Pieralisi" <lpieralisi@kernel•org>,
"Manivannan Sadhasivam" <mani@kernel•org>,
"Rob Herring" <robh@kernel•org>,
"Niklas Schnelle" <schnelle@linux•ibm.com>
Subject: Re: [PATCH] PCI: Fix endianness issues in pci_bus_read_config()
Date: Thu, 31 Jul 2025 21:01:17 +0200 [thread overview]
Message-ID: <6e34b4af-dff9-4360-b3da-c95ca7c740c9@app.fastmail.com> (raw)
In-Reply-To: <20250731183944.GA3424583@bhelgaas>
On Thu, Jul 31, 2025, at 20:39, Bjorn Helgaas wrote:
> On Thu, Jul 31, 2025 at 07:38:58PM +0200, Gerd Bayer wrote:
>>
>> - if (size == 1)
>> - return pci_bus_read_config_byte(bus, devfn, where, (u8 *)val);
>> - else if (size == 2)
>> - return pci_bus_read_config_word(bus, devfn, where, (u16 *)val);
>> - else if (size == 4)
>> - return pci_bus_read_config_dword(bus, devfn, where, val);
>> - else
>> - return PCIBIOS_BAD_REGISTER_NUMBER;
>> + if (size == 1) {
>> + rc = pci_bus_read_config_byte(bus, devfn, where, (u8 *)val);
>> +#if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
>> + *val = ((*val >> 24) & 0xff);
>> +#endif
>
> Yeah, this is all pretty ugly. Obviously the previous code in
> __pci_find_next_cap_ttl() didn't need this. My guess is that was
> because the destination for the read data was always the correct type
> (u8/u16/u32), but here we always use a u32 and cast it to the
> appropriate type. Maybe we can use the correct types here instead of
> the casts?
Agreed, the casts here just add more potential for bugs.
The pci_bus_read_config() interface itself may have been a
mistake, can't the callers just use the underlying helpers
directly?
Arnd
next prev parent reply other threads:[~2025-07-31 19:01 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20250716231121.GA2564572@bhelgaas>
2025-07-31 7:32 ` [REGRESSION] next/master: suspect endianness issue in common PCI capability search macro Gerd Bayer
2025-07-31 17:38 ` [PATCH] PCI: Fix endianness issues in pci_bus_read_config() Gerd Bayer
2025-07-31 18:39 ` Bjorn Helgaas
2025-07-31 19:01 ` Arnd Bergmann [this message]
2025-08-01 8:18 ` Manivannan Sadhasivam
2025-08-01 9:25 ` Hans Zhang
2025-08-01 9:47 ` Manivannan Sadhasivam
2025-08-01 10:06 ` Hans Zhang
2025-08-01 10:54 ` Manivannan Sadhasivam
2025-08-01 11:30 ` Gerd Bayer
2025-08-01 16:54 ` Hans Zhang
2025-08-01 18:08 ` Keith Busch
2025-08-02 15:23 ` Hans Zhang
2025-08-02 15:40 ` Arnd Bergmann
2025-08-04 3:06 ` Hans Zhang
2025-08-04 8:03 ` Arnd Bergmann
2025-08-04 8:25 ` Hans Zhang
2025-08-04 10:09 ` Gerd Bayer
2025-08-12 14:44 ` Hans Zhang
2025-08-13 7:47 ` Niklas Schnelle
2025-08-13 7:50 ` Hans Zhang
2025-08-04 14:33 ` Bjorn Helgaas
2025-08-04 15:04 ` Hans Zhang
2025-08-01 16:47 ` Hans Zhang
2025-07-31 18:53 ` Lukas Wunner
2025-08-01 7:52 ` Geert Uytterhoeven
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