[PATCH 0/2] drm/vkms: Introduce basic support for configfs

[Rodrigo Siqueira]

This patchset introduces the support for configfs in vkms by adding a
primary structure for handling the vkms subsystem and exposing
connectors as a use case.  This series allows enabling/disabling virtual
and writeback connectors on the fly. The first patch of this series
reworks the initialization and cleanup code of each type of connector,
with this change, the second patch adds the configfs support for vkms.
It is important to highlight that this patchset depends on
https://patchwork.freedesktop.org/series/61738/.

After applying this series, the user can utilize these features with the
following steps:

1. Load vkms without parameter

  modprobe vkms

2. Mount a configfs filesystem

  mount -t configfs none /mnt/

After that, the vkms subsystem will look like this:

vkms/
 |__connectors
    |__Virtual
        |__ enable

The connectors directories have information related to connectors, and
as can be seen, the virtual connector is enabled by default. Inside a
connector directory (e.g., Virtual) has an attribute named ‘enable’
which is used to enable and disable the target connector. For example,
the Virtual connector has the enable attribute set to 1. If the user
wants to enable the writeback connector it is required to use the mkdir
command, as follows:

  cd /mnt/vkms/connectors
  mkdir Writeback

After the above command, the writeback connector will be enabled, and
the user could see the following tree:

vkms/
 |__connectors
    |__Virtual
    |   |__ enable
    |__Writeback
        |__ enable

If the user wants to remove the writeback connector, it is required to
use the command rmdir, for example

  rmdir Writeback

Another way to enable and disable a connector it is by using the enable
attribute, for example, we can disable the Virtual connector with:

  echo 0 > /mnt/vkms/connectors/Virtual/enable

And enable it again with:

  echo 1 > /mnt/vkms/connectors/Virtual/enable

It is important to highlight that configfs 'obey' the parameters used
during the vkms load and does not allow users to remove a connector
directory if it was load via module parameter. For example:

  modprobe vkms enable_writeback=1

vkms/
 |__connectors
    |__Virtual
    |   |__ enable
    |__Writeback
        |__ enable

If the user tries to remove the Writeback connector with “rmdir
Writeback”, the operation will be not permitted because the Writeback
connector was loaded with the modules. However, the user may disable the
writeback connector with:

  echo 0 > /mnt/vkms/connectors/Writeback/enable


Rodrigo Siqueira (2):
  drm/vkms: Add enable/disable functions per connector
  drm/vkms: Introduce configfs for enabling/disabling connectors

 drivers/gpu/drm/vkms/Makefile         |   3 +-
 drivers/gpu/drm/vkms/vkms_configfs.c  | 229 ++++++++++++++++++++++++++
 drivers/gpu/drm/vkms/vkms_drv.c       |   6 +
 drivers/gpu/drm/vkms/vkms_drv.h       |  17 ++
 drivers/gpu/drm/vkms/vkms_output.c    |  84 ++++++----
 drivers/gpu/drm/vkms/vkms_writeback.c |  31 +++-
 6 files changed, 332 insertions(+), 38 deletions(-)
 create mode 100644 drivers/gpu/drm/vkms/vkms_configfs.c

-- 
2.21.0


-- 
Rodrigo Siqueira
https://siqueira.tech