Re: [Intel-gfx] [PATCH 11/21] fbcon: Extract fbcon_open/release helpers

Sam Ravnborg
2022-02-03T21:15:25Z

Hi Daniel,

On Mon, Jan 31, 2022 at 10:05:42PM +0100, Daniel Vetter wrote:
> There's two minor behaviour changes in here:
> - in error paths we now consistently call fb_ops->fb_release
> - fb_release really can't fail (fbmem.c ignores it too) and there's no
> reasonable cleanup we can do anyway.
>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Claudio Suarez <cssk@net-c.es>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Cc: Du Cheng <ducheng2@gmail.com>
> ---
> drivers/video/fbdev/core/fbcon.c | 107 +++++++++++++++----------------
> 1 file changed, 53 insertions(+), 54 deletions(-)
>
> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> index fa30e1909164..eea2ee14b64c 100644
> --- a/drivers/video/fbdev/core/fbcon.c
> +++ b/drivers/video/fbdev/core/fbcon.c
> @@ -680,19 +680,37 @@ static int fbcon_invalid_charcount(struct fb_info *info, unsigned charcount)
>
> #endif /* CONFIG_MISC_TILEBLITTING */
>
> +static int fbcon_open(struct fb_info *info)
> +{
> + if (!try_module_get(info->fbops->owner))
> + return -ENODEV;
> +
> + if (info->fbops->fb_open &&
> + info->fbops->fb_open(info, 0)) {
> + module_put(info->fbops->owner);
> + return -ENODEV;
> + }
> +
> + return 0;
> +}
> +
> +static void fbcon_release(struct fb_info *info)
> +{
> + if (info->fbops->fb_release)
> + info->fbops->fb_release(info, 0);
> +
> + module_put(info->fbops->owner);
> +}
>
> static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
> int unit, int oldidx)
> {
> struct fbcon_ops *ops = NULL;
> - int err = 0;
> -
> - if (!try_module_get(info->fbops->owner))
> - err = -ENODEV;
> + int err;
>
> - if (!err && info->fbops->fb_open &&
> - info->fbops->fb_open(info, 0))
> - err = -ENODEV;
> + err = fbcon_open(info);
> + if (err)
> + return err;
>
> if (!err) {
> ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
> @@ -713,7 +731,7 @@ static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
>
> if (err) {
> con2fb_map[unit] = oldidx;
> - module_put(info->fbops->owner);
> + fbcon_release(info);
> }
>
> return err;
> @@ -724,45 +742,34 @@ static int con2fb_release_oldinfo(struct vc_data *vc, struct fb_info *oldinfo,
> int oldidx, int found)
> {
> struct fbcon_ops *ops = oldinfo->fbcon_par;
> - int err = 0, ret;
> + int ret;
>
> - if (oldinfo->fbops->fb_release &&
> - oldinfo->fbops->fb_release(oldinfo, 0)) {
> - con2fb_map[unit] = oldidx;
The old code assigns con2fb_map[unit] before is calls
newinfo->fbops->fb_release).
I wonder if there can be any callback to fbcon where the value
of con2fb_map[unit] matters?

> - if (!found && newinfo->fbops->fb_release)
> - newinfo->fbops->fb_release(newinfo, 0);
> - if (!found)
> - module_put(newinfo->fbops->owner);
> - err = -ENODEV;
> - }
> + fbcon_release(oldinfo);
>
> - if (!err) {
> - fbcon_del_cursor_work(oldinfo);
> - kfree(ops->cursor_state.mask);
> - kfree(ops->cursor_data);
> - kfree(ops->cursor_src);
> - kfree(ops->fontbuffer);
> - kfree(oldinfo->fbcon_par);
> - oldinfo->fbcon_par = NULL;
> - module_put(oldinfo->fbops->owner);
> - /*
> - If oldinfo and newinfo are driving the same hardware,
> - the fb_release() method of oldinfo may attempt to
> - restore the hardware state. This will leave the
> - newinfo in an undefined state. Thus, a call to
> - fb_set_par() may be needed for the newinfo.
> - */
> - if (newinfo && newinfo->fbops->fb_set_par) {
> - ret = newinfo->fbops->fb_set_par(newinfo);
> + fbcon_del_cursor_work(oldinfo);

> + kfree(ops->cursor_state.mask);
> + kfree(ops->cursor_data);
> + kfree(ops->cursor_src);
> + kfree(ops->fontbuffer);
> + kfree(oldinfo->fbcon_par);
> + oldinfo->fbcon_par = NULL;
These all look like candidates to stuff into fbcon_release()
That would drop the nice symmetry but make it more consistent.

I think we miss freeing ops->cursor_data in fbcon_exit(),
but I did not follow all the code.

With my ramblings considered the patch is
Acked-by: Sam Ravnborg <sam@ravnborg.org>

Sam

> + /*
> + If oldinfo and newinfo are driving the same hardware,
> + the fb_release() method of oldinfo may attempt to
> + restore the hardware state. This will leave the
> + newinfo in an undefined state. Thus, a call to
> + fb_set_par() may be needed for the newinfo.
> + */
> + if (newinfo && newinfo->fbops->fb_set_par) {
> + ret = newinfo->fbops->fb_set_par(newinfo);
>
> - if (ret)
> - printk(KERN_ERR "con2fb_release_oldinfo: "
> - "detected unhandled fb_set_par error, "
> - "error code %d\n", ret);
> - }
> + if (ret)
> + printk(KERN_ERR "con2fb_release_oldinfo: "
> + "detected unhandled fb_set_par error, "
> + "error code %d\n", ret);
> }
>
> - return err;
> + return 0;
> }
>
> static void con2fb_init_display(struct vc_data *vc, struct fb_info *info,
> @@ -917,7 +924,6 @@ static const char *fbcon_startup(void)
> struct fbcon_display *p = &fb_display[fg_console];
> struct vc_data *vc = vc_cons[fg_console].d;
> const struct font_desc *font = NULL;
> - struct module *owner;
> struct fb_info *info = NULL;
> struct fbcon_ops *ops;
> int rows, cols;
> @@ -936,17 +942,12 @@ static const char *fbcon_startup(void)
> if (!info)
> return NULL;
>
> - owner = info->fbops->owner;
> - if (!try_module_get(owner))
> + if (fbcon_open(info))
> return NULL;
> - if (info->fbops->fb_open && info->fbops->fb_open(info, 0)) {
> - module_put(owner);
> - return NULL;
> - }
>
> ops = kzalloc(sizeof(struct fbcon_ops), GFP_KERNEL);
> if (!ops) {
> - module_put(owner);
> + fbcon_release(info);
> return NULL;
> }
>
> @@ -3331,10 +3332,6 @@ static void fbcon_exit(void)
> }
>
> if (mapped) {
> - if (info->fbops->fb_release)
> - info->fbops->fb_release(info, 0);
> - module_put(info->fbops->owner);
> -
> if (info->fbcon_par) {
> struct fbcon_ops *ops = info->fbcon_par;
>
> @@ -3344,6 +3341,8 @@ static void fbcon_exit(void)
> kfree(info->fbcon_par);
> info->fbcon_par = NULL;
> }
> +
> + fbcon_release(info);
> }
> }
> }
> --
> 2.33.0