Re: [PATCH RFC v1 00/52] drm/crtc: Rename struct drm_crtc::dev to drm_dev

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

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On Thu, Jul 13, 2023 at 12:03:05PM +0300, Jani Nikula wrote:
> On Wed, 12 Jul 2023, Uwe Kleine-König <u.kleine-koenig@pengutronix.de> wrote:
> > Hello Jani,
> >
> > On Wed, Jul 12, 2023 at 05:34:28PM +0300, Jani Nikula wrote:
> >> On Wed, 12 Jul 2023, Uwe Kleine-König <u.kleine-koenig@pengutronix.de> wrote:
> >> > Hello,
> >> >
> >> > while I debugged an issue in the imx-lcdc driver I was constantly
> >> > irritated about struct drm_device pointer variables being named "dev"
> >> > because with that name I usually expect a struct device pointer.
> >> >
> >> > I think there is a big benefit when these are all renamed to "drm_dev".
> >> > I have no strong preference here though, so "drmdev" or "drm" are fine
> >> > for me, too. Let the bikesheding begin!
> >> >
> >> > Some statistics:
> >> >
> >> > $ git grep -ohE 'struct drm_device *\* *[^ (),;]*' v6.5-rc1 | sort | uniq -c | sort -n
> >> >       1 struct drm_device *adev_to_drm
> >> >       1 struct drm_device *drm_
> >> >       1 struct drm_device          *drm_dev
> >> >       1 struct drm_device        *drm_dev
> >> >       1 struct drm_device *pdev
> >> >       1 struct drm_device *rdev
> >> >       1 struct drm_device *vdev
> >> >       2 struct drm_device *dcss_drv_dev_to_drm
> >> >       2 struct drm_device **ddev
> >> >       2 struct drm_device *drm_dev_alloc
> >> >       2 struct drm_device *mock
> >> >       2 struct drm_device *p_ddev
> >> >       5 struct drm_device *device
> >> >       9 struct drm_device * dev
> >> >      25 struct drm_device *d
> >> >      95 struct drm_device *
> >> >     216 struct drm_device *ddev
> >> >     234 struct drm_device *drm_dev
> >> >     611 struct drm_device *drm
> >> >    4190 struct drm_device *dev
> >> >
> >> > This series starts with renaming struct drm_crtc::dev to drm_dev. If
> >> > it's not only me and others like the result of this effort it should be
> >> > followed up by adapting the other structs and the individual usages in
> >> > the different drivers.
> >> 
> >> I think this is an unnecessary change. In drm, a dev is usually a drm
> >> device, i.e. struct drm_device *.
> >
> > Well, unless it's not. Prominently there is
> >
> > 	struct drm_device {
> > 		...
> > 		struct device *dev;
> > 		...
> > 	};
> >
> > which yields quite a few code locations using dev->dev which is
> > IMHO unnecessary irritating:
> >
> > 	$ git grep '\<dev->dev' v6.5-rc1 drivers/gpu/drm | wc -l
> > 	1633
> >
> > Also the functions that deal with both a struct device and a struct
> > drm_device often use "dev" for the struct device and then "ddev" for
> > the drm_device (see for example amdgpu_device_get_pcie_replay_count()).
> 
> Why is specifically struct drm_device *dev so irritating to you?
> 
> You lead us to believe it's an outlier in kernel, something that goes
> against common kernel style, but it's really not:
> 
> $ git grep -how "struct [A-Za-z0-9_]\+ \*dev" | sort | uniq -c | sort -rn | head -20
>   38494 struct device *dev
>   16388 struct net_device *dev
>    4184 struct drm_device *dev
>    2780 struct pci_dev *dev
>    1916 struct comedi_device *dev
>    1510 struct mlx5_core_dev *dev
>    1057 struct mlx4_dev *dev
>     894 struct b43_wldev *dev
>     762 struct input_dev *dev
>     623 struct usbnet *dev
>     561 struct mlx5_ib_dev *dev
>     525 struct mt76_dev *dev
>     465 struct mt76x02_dev *dev
>     435 struct platform_device *dev
>     431 struct usb_device *dev
>     411 struct mt7915_dev *dev
>     398 struct cx231xx *dev
>     378 struct mei_device *dev
>     363 struct ksz_device *dev
>     359 struct mthca_dev *dev
> 
> A good portion of the above also have a dev member.

Yeah, other subsystems and drivers have the same problem. You're lucky
that I noticed drm first and invested some effort to improve it. IMHO
other subsystems being bad shouldn't stop drm to improve here.

And note that for example for pci_dev there are 5794 instances that are
named "pdev" and there are 9971 struct platform_device that are called
"pdev", too. So the majority for these does it better. And agreed,
net_device and others are also inconsistent. If you want an area that is
better, look at the naming of i2c_client or spi_device. (And take into
account that these are spread all over the tree and so are not in
control of a single maintainer team.)

> Are you planning on changing all of the above too, or are you only
> annoyed by drm?

Would you be more welcoming if I promised to tackle some of the above,
too? If so: I might. I hesitate a bit because I didn't suffer from the
others. (Apart from asking ctags for "dev" is a nightmare.)

And regarding the second part of your question: I was annoyed by drm
because that was the one that offended me while researching a problem in
a drm driver. And the variable/struct member name irritated me enough to
believe that with consistent naming I would have found it quicker.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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