linux-kernel - Re: [PATCH] drm: sysfs: Add to get current mode

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Date:   Wed, 5 Aug 2020 13:26:55 +0200
From:   daniel@...ll.ch
To:     unlisted-recipients:; (no To-header on input)
Cc:     Daniel Vetter <daniel@...ll.ch>,
        Heiko Stübner <heiko@...ech.de>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Tao Huang <huangtao@...k-chips.com>,
        Andy Yan <andy.yan@...k-chips.com>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Kever Yang <kever.yang@...k-chips.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm: sysfs: Add to get current mode

On Wed, Aug 05, 2020 at 06:03:15PM +0800, Huang Jiachai wrote:
> Hi Daniel
> 
> 在 2020/8/5 17:36, Daniel Vetter 写道:
> > On Wed, Aug 5, 2020 at 10:37 AM Sandy Huang <hjc@...k-chips.com> wrote:
> > > add this node to get the current true mode.
> > > 
> > > Signed-off-by: Sandy Huang <hjc@...k-chips.com>
> > Uh what's this for? Since it's sysfs, I guess there's something
> > parsing this, which means we'd kinda need to have that piece too.
> > 
> > If it's just for debugging purposes, then we already have this
> > information in debugfs, together with everything else that's in the
> > atomic modeset state.
> > -Daniel
> 
> yes, this is just for debug;
> 
> and i get the information what i need from cat
> /sys/kernel/debug/dri/0/state, thanks.

Cool, sounds like this is resolved. And if you need any additional debug
information about display state, then best to extend that file. It comes
with driver hooks, so that you can include any additional driver stuff, or
outright read out registers and everything.

Cheers, Daniel

> 
> > > ---
> > >   drivers/gpu/drm/drm_sysfs.c | 30 ++++++++++++++++++++++++++++++
> > >   1 file changed, 30 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
> > > index 939f0032aab1..f39bcd34853b 100644
> > > --- a/drivers/gpu/drm/drm_sysfs.c
> > > +++ b/drivers/gpu/drm/drm_sysfs.c
> > > @@ -19,6 +19,7 @@
> > >   #include <linux/slab.h>
> > > 
> > >   #include <drm/drm_connector.h>
> > > +#include <drm/drm_crtc.h>
> > >   #include <drm/drm_device.h>
> > >   #include <drm/drm_file.h>
> > >   #include <drm/drm_modes.h>
> > > @@ -236,16 +237,45 @@ static ssize_t modes_show(struct device *device,
> > >          return written;
> > >   }
> > > 
> > > +static ssize_t current_mode_show(struct device *device,
> > > +                     struct device_attribute *attr,
> > > +                     char *buf)
> > > +{
> > > +       struct drm_connector *connector = to_drm_connector(device);
> > > +       struct drm_display_mode *mode;
> > > +       struct drm_crtc_state *crtc_state;
> > > +       bool interlaced;
> > > +       int written = 0;
> > > +
> > > +       if (!connector->state || !connector->state->crtc)
> > > +               return written;
> > > +
> > > +       crtc_state = connector->state->crtc->state;
> > > +       if (!crtc_state)
> > > +               return written;
> > > +
> > > +       mode = &crtc_state->mode;
> > > +
> > > +       interlaced = !!(mode->flags & DRM_MODE_FLAG_INTERLACE);
> > > +       written += snprintf(buf + written, PAGE_SIZE - written, "%dx%d%s%d\n",
> > > +                           mode->hdisplay, mode->vdisplay,
> > > +                           interlaced ? "i" : "p", drm_mode_vrefresh(mode));
> > > +
> > > +       return written;
> > > +}
> > > +
> > >   static DEVICE_ATTR_RW(status);
> > >   static DEVICE_ATTR_RO(enabled);
> > >   static DEVICE_ATTR_RO(dpms);
> > >   static DEVICE_ATTR_RO(modes);
> > > +static DEVICE_ATTR_RO(current_mode);
> > > 
> > >   static struct attribute *connector_dev_attrs[] = {
> > >          &dev_attr_status.attr,
> > >          &dev_attr_enabled.attr,
> > >          &dev_attr_dpms.attr,
> > >          &dev_attr_modes.attr,
> > > +       &dev_attr_current_mode.attr,
> > >          NULL
> > >   };
> > > 
> > > --
> > > 2.17.1
> > > 
> > > 
> > > 
> > 
> -- 
> Best Regard
> 
> 黄家钗
> Sandy Huang
> Addr: 福州市鼓楼区铜盘路软件大道89号福州软件园A区21号楼(350003)
>       No. 21 Building, A District, No.89,software Boulevard Fuzhou,Fujian,PRC
> Tel：+86 0591-87884919  8690
> E-mail：hjc@...k-chips.com
> 
> 
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch