From: Gerd Hoffmann <kraxel@redhat.com>
To: Thomas Zimmermann <tzimmermann@suse.de>
Cc: dri-devel@lists.freedesktop.org,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH] drm/bochs: Add screen blanking support
Date: Wed, 21 Apr 2021 09:19:42 +0200 [thread overview]
Message-ID: <20210421071942.eyzbao63pn54loj2@sirius.home.kraxel.org> (raw)
In-Reply-To: <6d2f59c0-113f-2d9e-1fb3-a794dafbd74a@suse.de>
> > However, a tricky part is that the QEMU vga code does treat VGA_ATT_IW
> > register always as "flip-flop"; the first write is for index and the
> > second write is for the data like palette. Meanwhile, in the current
> > bochs DRM driver, the flip-flop wasn't considered, and it calls only
> > the register update once with the value 0x20.
> >
>
> Unless bochs does things very different, the index should first be reset by
> reading 0x3da. Then write the index, then the data.
>
> https://web.stanford.edu/class/cs140/projects/pintos/specs/freevga/vga/vgareg.htm#attribute
bochs should follow standard vga logic here.
Also a bochs_set_blank(true/false) helper function probably makes sense.
take care,
Gerd
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next prev parent reply other threads:[~2021-04-21 7:19 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-20 16:56 [PATCH] drm/bochs: Add screen blanking support Takashi Iwai
2021-04-20 17:47 ` Thomas Zimmermann
2021-04-21 7:19 ` Gerd Hoffmann [this message]
2021-04-21 8:02 ` Takashi Iwai
2021-04-21 8:01 ` Takashi Iwai
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