From: Laszlo Ersek <lersek@redhat.com>
To: "Marvin Häuser" <Marvin.Haeuser@outlook.com>
Cc: "edk2-devel@lists.01.org" <edk2-devel@lists.01.org>
Subject: Re: PciLib/PciExpressLib: 64-bit r/w functions
Date: Sun, 6 Aug 2017 13:34:58 +0200 [thread overview]
Message-ID: <f6db0e77-2e46-6fb3-c623-704c83c4f71c@redhat.com> (raw)
In-Reply-To: <AM4PR06MB1491646EA6C1508EF74C6B2780B70@AM4PR06MB1491.eurprd06.prod.outlook.com>
On 08/05/17 23:38, Marvin H?user wrote:
> Dear developers,
>
> While browsing the KabylakeSiPkg code, I noticed that 64-bit registers are read directly via MmioRead64() as there is no PciRead64() function.
> Is there a specific reason there are no PciRead64() and PciExpressRead64() functions or were they simply not needed previously?
Validity of 64-bit accesses to PCI config space is platform dependent
[*] and I guess the PciLib designers didn't want to deviate from the
common interface pattern that PciReadXX() always succeeds (as long as
the input parameter is valid), regardless of XX.
[*] The UEFI spec repeats the following paragraph in several places:
The I/O operations are carried out exactly as requested. The caller
is responsible satisfying any alignment and I/O width restrictions
that the PCI controller on a platform might require. For example on
some platforms, width requests of EfiPciIoWidthUint64 do not work.
Thanks
Laszlo
next prev parent reply other threads:[~2017-08-06 11:32 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-05 21:38 PciLib/PciExpressLib: 64-bit r/w functions Marvin H?user
2017-08-06 11:34 ` Laszlo Ersek [this message]
2017-08-06 12:46 ` Marvin Häuser
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