From: Guenter Roeck <linux@roeck-us.net>
To: sashiko-reviews@lists.linux.dev, Jihong Min <hurryman2212@gmail.com>
Cc: linux-hwmon@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH v5 1/2] usb: xhci-pci: add AMD Promontory 21 PCI glue
Date: Wed, 13 May 2026 18:20:55 -0700 [thread overview]
Message-ID: <110e9a0d-bc91-4959-8a7b-1a055d0b49f7@roeck-us.net> (raw)
In-Reply-To: <20260514004055.1BBCAC19425@smtp.kernel.org>
On 5/13/26 17:40, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
> - [High] The Kconfig dependency `depends on USB_XHCI_PCI=y` completely disables PROM21 support for systems where the core driver is built as a module.
> - [Low] Signed integer overflow when calculating the auxiliary device ID.
> --
>
> commit 20f4e35b2f88ebe2b8988b4f07fe7cc28199096b
> Author: Jihong Min <hurryman2212@gmail.com>
> Subject: usb: xhci-pci: add AMD Promontory 21 PCI glue
>
> This commit adds a small PCI glue driver for AMD Promontory 21 xHCI
> controllers. It binds the controllers, delegates USB host operation to
> the common xHCI PCI core, and creates an auxiliary device for optional
> temperature sensor support.
>
>> diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig
>> --- a/drivers/usb/host/Kconfig
>> +++ b/drivers/usb/host/Kconfig
>
> [ ... ]
>
>> @@ -42,6 +42,26 @@ config USB_XHCI_PCI
>> depends on USB_PCI
>> default y
>>
>> +config USB_XHCI_PCI_PROM21
>> + bool "AMD Promontory 21 xHCI PCI support"
>> + depends on X86
>> + depends on USB_XHCI_PCI=y
>
> Does depending strictly on USB_XHCI_PCI=y cause a configuration regression
> for most distributions where the core driver is configured as a module?
>
> The driver source appears fully capable of being built as a module, using
> module-related macros and module_pci_driver().
>
> If the intent is to prevent an early boot mismatch where xhci-pci is
> built-in but the PROM21 glue is a module, could this instead be a tristate
> option using depends on USB_XHCI_PCI and depends on !(USB_XHCI_PCI=y && m)?
> This would enforce the boot constraint while preserving support for modular
> kernel builds.
>
That makes sense to me. That would be stronger than using default (which
was my idea of dealing with the problem). Restricting the code to USB_XHCI_PCI=y
seems to be a bit extreme.
> [ ... ]
>
>> diff --git a/drivers/usb/host/xhci-pci-prom21.c b/drivers/usb/host/xhci-pci-prom21.c
>> --- /dev/null
>> +++ b/drivers/usb/host/xhci-pci-prom21.c
>
> [ ... ]
>
>> +static int prom21_xhci_create_auxdev(struct pci_dev *pdev)
>> +{
>> + struct prom21_xhci_auxdev *prom21_auxdev;
>> + struct usb_hcd *hcd = pci_get_drvdata(pdev);
>
> [ ... ]
>
>> + prom21_auxdev->auxdev =
>> + auxiliary_device_create(&pdev->dev, KBUILD_MODNAME, "hwmon",
>> + &prom21_auxdev->pdata,
>> + (pci_domain_nr(pdev->bus) << 16) |
>> + pci_dev_id(pdev));
>
> Does left-shifting pci_domain_nr() introduce a signed integer overflow
> regression?
>
> The function pci_domain_nr() returns a signed int, which can be up to 0xFFFF
> on ACPI systems. Left-shifting a value of 0x8000 or greater by 16 bits
> alters the sign bit of a 32-bit int, resulting in undefined behavior in C.
>
> Would casting the return value to an unsigned integer, such as
> (u32)pci_domain_nr(pdev->bus) << 16, avoid this overflow?
>
FWIW, I don't think that is a real problem. auxiliary_device_create()
takes an int as id parameter, so the result would be converted back to int
anyway. Maybe use "(pci_domain_nr(pdev->bus) & 0x7fff) << 16" instead,
but I don't know if that adds any practical value.
Thanks,
Guenter
next prev parent reply other threads:[~2026-05-14 1:20 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-12 21:39 [PATCH v5 0/2] AMD Promontory 21 xHCI temperature sensor support Jihong Min
2026-05-12 21:39 ` [PATCH v5 1/2] usb: xhci-pci: add AMD Promontory 21 PCI glue Jihong Min
2026-05-14 0:40 ` sashiko-bot
2026-05-14 1:20 ` Guenter Roeck [this message]
2026-05-14 13:38 ` Jihong Min
2026-05-14 13:44 ` Jihong Min
2026-05-15 1:49 ` Guenter Roeck
2026-05-14 14:29 ` Jihong Min
2026-05-14 19:22 ` Guenter Roeck
2026-05-12 21:39 ` [PATCH v5 2/2] hwmon: add AMD Promontory 21 xHCI temperature sensor support Jihong Min
2026-05-14 1:00 ` sashiko-bot
2026-05-14 1:13 ` Guenter Roeck
2026-05-12 21:49 ` [PATCH v5 0/2] " Jihong Min
2026-05-13 14:48 ` Mario Limonciello
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