On Thu, Jun 05, 2025 at 08:28:20PM +0200, Jean Delvare wrote:
> Casting the PCI device class to a signed 8-bit type before extending
> it to a 16-bit type causes the sign bit to replicate to the whole
> upper byte. For example, a sub-class value of 0x80 ends up being
> displayed as 0xFF80.
>
> It doesn't make sense to display an 8-bit value using a 16-bit format
> in the first place anyway. Simplify the code and directly display the
> 8-bit PCI device class and sub-class values as-is.
>
> Fixes: 3e86b5d3a228 ("dmioem: Decode HPE OEM Record 203")
> Signed-off-by: Jean Delvare <[email protected]>
> ---
> The sign extension does not happen on all architectures, it depends
> whether "char" is considered signed or not. This makes the code not
> portable and this is how I noticed the problem.
>
> An alternative fix would be to display the PCI device class as a
> whole as one 16-bit number (as lspci is doing) instead of splitting it
> into a class code and a sub class code.
>
> As a side note, I wonder if we should get rid of dmi_hp_203_pciinfo()
> altogether. Whether the device is present or not was already tested
> before, testing it again is redundant and should not be needed. I
> checked on my collection of dumps and it indeed made no difference.
I have a single counter example of an ML150 Gen 9 where using the proposed
patch:
./dmidecode -t 203 --from-dump
/home/hoemann/Work/tools/dmidecode/dump2/ML150G9.dmi
...
Handle 0x00B9, DMI type 203, 34 bytes
HP Device Correlation Record
Associated Device Record: 0x009E
Associated SMBus Record: N/A
PCI Vendor ID: 0x103c
PCI Device ID: 0x193f
PCI Sub Vendor ID: 0x103c
PCI Sub Device ID: 0x3381
PCI Class Code: 0xff
PCI Sub Class Code: 0x00
So, such situations exists.
This is from 2017 Bios and might be a bios defect. I know the owner
of this particular system and will get an updated dump to see if issue
remains.
>
> dmioem.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> --- dmidecode.orig/dmioem.c
> +++ dmidecode/dmioem.c
> @@ -1205,8 +1205,8 @@ static int dmi_decode_hp(const struct dm
> dmi_hp_203_pciinfo("PCI Device ID", WORD(data +
> 0x0A));
> dmi_hp_203_pciinfo("PCI Sub Vendor ID",
> WORD(data + 0x0C));
> dmi_hp_203_pciinfo("PCI Sub Device ID",
> WORD(data + 0x0E));
> - dmi_hp_203_pciinfo("PCI Class Code",
> (char)data[0x10]);
> - dmi_hp_203_pciinfo("PCI Sub Class Code",
> (char)data[0x11]);
> + pr_attr("PCI Class Code", "0x%02x", data[0x10]);
> + pr_attr("PCI Sub Class Code", "0x%02x",
> data[0x11]);
> }
> dmi_hp_203_assoc_hndl("Parent Handle", WORD(data +
> 0x12));
> pr_attr("Flags", "0x%04X", WORD(data + 0x14));
>
> --
> Jean Delvare
> SUSE L3 Support
--
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Jerry Hoemann Software Engineer Hewlett Packard Enterprise
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