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Message-ID: <6d287bbb1733814009dfeb7d48f08cb6f44dc56c.camel@pengutronix.de>
Date: Wed, 21 Jun 2023 12:23:35 +0200
From: Lucas Stach <l.stach@...gutronix.de>
To: Sui Jingfeng <suijingfeng@...ngson.cn>,
Sui Jingfeng <18949883232@....com>,
Russell King <linux+etnaviv@...linux.org.uk>,
Christian Gmeiner <christian.gmeiner@...il.com>,
David Airlie <airlied@...il.com>,
Daniel Vetter <daniel@...ll.ch>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
Philipp Zabel <p.zabel@...gutronix.de>,
linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
etnaviv@...ts.freedesktop.org
Subject: Re: [PATCH v10 03/11] drm/etnaviv: Add dedicated functions to
create and destroy platform device
Am Mittwoch, dem 21.06.2023 um 17:49 +0800 schrieb Sui Jingfeng:
> Hi
>
> On 2023/6/21 17:15, Lucas Stach wrote:
> > Am Dienstag, dem 20.06.2023 um 17:47 +0800 schrieb Sui Jingfeng:
> > > From: Sui Jingfeng <suijingfeng@...ngson.cn>
> > >
> > > Also rename the virtual master platform device as etnaviv_platform_device,
> > > for better reflection that it is a platform device, not a DRM device.
> > >
> > > Another benefit is that we no longer need to call of_node_put() for three
> > > different cases, Instead, we only need to call it once.
> > >
> > > Cc: Lucas Stach <l.stach@...gutronix.de>
> > > Cc: Christian Gmeiner <christian.gmeiner@...il.com>
> > > Cc: Philipp Zabel <p.zabel@...gutronix.de>
> > > Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> > > Cc: Daniel Vetter <daniel@...ll.ch>
> > > Signed-off-by: Sui Jingfeng <suijingfeng@...ngson.cn>
> > > ---
> > > drivers/gpu/drm/etnaviv/etnaviv_drv.c | 56 +++++++++++++++++++--------
> > > 1 file changed, 39 insertions(+), 17 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_drv.c b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> > > index 31a7f59ccb49..cec005035d0e 100644
> > > --- a/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> > > +++ b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> > > @@ -656,12 +656,44 @@ static struct platform_driver etnaviv_platform_driver = {
> > > },
> > > };
> > >
> > > -static struct platform_device *etnaviv_drm;
> > > +static struct platform_device *etnaviv_platform_device;
> > >
> > > -static int __init etnaviv_init(void)
> > > +static int etnaviv_create_platform_device(const char *name,
> > > + struct platform_device **ppdev)
> > As the platform device is a global static variable, there is no need to
> > push it through the parameters of this function. Just use the global
> > variable directly in this function.
>
> A function reference a global static variable is *NOT* a *pure* fucntion,
>
That's right, but all you do with those indirections through the
parameter list is move which of the functions is non-pure, in your case
it's etnaviv_init/etnaviv_exit, with the indirection dropped it's
etnaviv_create_platform_device/etnaviv_destroy_platform_device.
> it degenerate as a procedure,
>
>
> The function is perfect in the sense that it does not reference any
> global variable.
>
>
> etnaviv_create_platform_device() is NOT intended to used by one function,
>
> a specific purpose only, but when create this function, I want to create other
>
> platform device with this function.
>
> Say, You want to create a dummy platform device, targeting to bind to the real master
>
> (the single GPU core) . To verify the idea that we choose the first 3D gpu core as master,
>
> other 2D or VG gpu core is not as important as the 3D one.
>
> The should bind to the 3D GPU core (master).
>
Sorry, I'm not following what you are trying to tell me here. Could you
please rephrase?
>
> While back to the question you ask, I want etnaviv_create_platform_device() to be generic,
>
> can be used by multiple place for multiple purpose.
>
> I have successfully copy this to a another drm driver by simply renaming.
>
> The body of the function itself does not need to change.
But it isn't shared, in this compilation unit this function is specific
to the etnaviv driver and I don't see why we shouldn't have etnaviv
specifics in there if it makes the code of this driver easier to
follow.
Regards,
Lucas
>
> > > {
> > > struct platform_device *pdev;
> > > int ret;
> > > +
> > > + pdev = platform_device_alloc(name, PLATFORM_DEVID_NONE);
> > > + if (!pdev)
> > > + return -ENOMEM;
> > > +
> > > + ret = platform_device_add(pdev);
> > > + if (ret) {
> > > + platform_device_put(pdev);
> > > + return ret;
> > > + }
> > > +
> > > + *ppdev = pdev;
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static void etnaviv_destroy_platform_device(struct platform_device **ppdev)
> > > +{
> > > + struct platform_device *pdev = *ppdev;
> > Same here, just use the global variable directly.
> >
> > Regards,
> > Lucas
> >
> > > +
> > > + if (!pdev)
> > > + return;
> > > +
> > > + platform_device_unregister(pdev);
> > > +
> > > + *ppdev = NULL;
> > > +}
> > > +
> > > +static int __init etnaviv_init(void)
> > > +{
> > > + int ret;
> > > struct device_node *np;
> > >
> > > etnaviv_validate_init();
> > > @@ -681,23 +713,13 @@ static int __init etnaviv_init(void)
> > > for_each_compatible_node(np, NULL, "vivante,gc") {
> > > if (!of_device_is_available(np))
> > > continue;
> > > + of_node_put(np);
> > >
> > > - pdev = platform_device_alloc("etnaviv", PLATFORM_DEVID_NONE);
> > > - if (!pdev) {
> > > - ret = -ENOMEM;
> > > - of_node_put(np);
> > > - goto unregister_platform_driver;
> > > - }
> > > -
> > > - ret = platform_device_add(pdev);
> > > - if (ret) {
> > > - platform_device_put(pdev);
> > > - of_node_put(np);
> > > + ret = etnaviv_create_platform_device("etnaviv",
> > > + &etnaviv_platform_device);
> > > + if (ret)
> > > goto unregister_platform_driver;
> > > - }
> > >
> > > - etnaviv_drm = pdev;
> > > - of_node_put(np);
> > > break;
> > > }
> > >
> > > @@ -713,7 +735,7 @@ module_init(etnaviv_init);
> > >
> > > static void __exit etnaviv_exit(void)
> > > {
> > > - platform_device_unregister(etnaviv_drm);
> > > + etnaviv_destroy_platform_device(&etnaviv_platform_device);
> > > platform_driver_unregister(&etnaviv_platform_driver);
> > > platform_driver_unregister(&etnaviv_gpu_driver);
> > > }
>
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