From: Bjorn Helgaas <helgaas@kernel.org>
To: Huacai Chen <chenhuacai@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
Daniel Vetter <daniel@ffwll.ch>,
Greg KH <gregkh@linuxfoundation.org>,
David Airlie <airlied@linux.ie>,
Maling list - DRI developers <dri-devel@lists.freedesktop.org>,
Xuefeng Li <lixuefeng@loongson.cn>,
Huacai Chen <chenhuacai@loongson.cn>,
Linux PCI <linux-pci@vger.kernel.org>
Subject: Re: [PATCH] vgaarb: Call vga_arb_device_init() after PCI enumeration
Date: Sat, 5 Jun 2021 12:59:36 -0500 [thread overview]
Message-ID: <20210605175936.GA2309279@bjorn-Precision-5520> (raw)
In-Reply-To: <CAAhV-H6MCGXiO3EcZV2BZi91AiUNsu2aZ=e9g4e2tcVVNOLbfg@mail.gmail.com>
On Sat, Jun 05, 2021 at 10:02:05AM +0800, Huacai Chen wrote:
> On Sat, Jun 5, 2021 at 3:56 AM Bjorn Helgaas <helgaas@kernel.org> wrote:
> > On Fri, Jun 04, 2021 at 12:50:03PM +0800, Huacai Chen wrote:
> > > On Thu, Jun 3, 2021 at 2:31 AM Bjorn Helgaas <bhelgaas@google.com> wrote:
> > > > I think the simplest solution, which I suggested earlier [1],
> > > > would be to explicitly call vga_arbiter_add_pci_device()
> > > > directly from the PCI core when it enumerates a VGA device.
> > > > Then there's no initcall and no need for the
> > > > BUS_NOTIFY_ADD/DEL_DEVICE stuff. vga_arbiter_add_pci_device()
> > > > could set the default VGA device when it is enumerated, and
> > > > change the default device if we enumerate a "better" one. And
> > > > hotplug VGA devices would work automatically.
> > >
> > > Emm, It seems that your solution has some difficulties to remove
> > > the whole initcall(vga_arb_device_init): we call
> > > vga_arbiter_add_pci_device() in pci_bus_add_device(), the
> > > list_for_each_entry() loop can be moved to
> > > vga_arbiter_check_bridge_sharing(),
> > > vga_arb_select_default_device() can be renamed to
> > > vga_arb_update_default_device() and be called in
> > > vga_arbiter_add_pci_device(), but how to handle
> > > misc_register(&vga_arb_device)?
> >
> > Might need to keep vga_arb_device_init() as an initcall, but
> > remove everything from it except the misc_register().
>
> OK, let me try. But I think call vga_arbiter_add_pci_device() in
> pci core is nearly the same as notifier. Anyway, I will send a new
> patch later.
Notifiers are useful in some situations, for example, if a loadable
module needs to be called when a device is added or removed.
But when possible, I will always choose a direct call instead because
it's much less complicated. The VGA arbiter cannot be a loadable
module, so I don't think there's any reason to use a notifier in this
case.
Bjorn
next prev parent reply other threads:[~2021-06-05 17:59 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210528082607.2015145-1-chenhuacai@loongson.cn>
[not found] ` <YLZYuM6SepbeLcI7@phenom.ffwll.local>
[not found] ` <YLZqe14Lf2+5Lbf3@kroah.com>
[not found] ` <YLZ2WJlHu0EZT7H9@phenom.ffwll.local>
[not found] ` <CAAhV-H5Mt7tmmDVoix6sY3UtfhjxGvHovve2N=5o5xtvmFeQOA@mail.gmail.com>
[not found] ` <YLewShl3lMyqJ1WZ@phenom.ffwll.local>
2021-06-02 18:31 ` [PATCH] vgaarb: Call vga_arb_device_init() after PCI enumeration Bjorn Helgaas
2021-06-02 19:26 ` Daniel Vetter
2021-06-04 4:50 ` Huacai Chen
2021-06-04 19:56 ` Bjorn Helgaas
2021-06-05 2:02 ` Huacai Chen
2021-06-05 17:59 ` Bjorn Helgaas [this message]
2021-06-12 4:40 ` Huacai Chen
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