[2/2] drm/edid: Have cea_db_offsets() zero start/end when the data block collection isn't found
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Message ID 20190902131546.4691-2-ville.syrjala@linux.intel.com
State New
Headers show
Series
  • [1/2] drm/edid: Don't look for CEA data blocks in CEA ext block rev < 3
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Commit Message

Ville Syrjälä Sept. 2, 2019, 1:15 p.m. UTC
From: Ville Syrjälä <ville.syrjala@linux.intel.com>

Let's make cea_db_offsets() a bit more convenient to use by
setting the start/end offsets to zero whenever the data block
collection isn't present. This makes it safe for the caller
to blindly iterate the data blocks even if there are none.

Cc: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/drm_edid.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Comments

Jean Delvare Sept. 10, 2019, 9:46 a.m. UTC | #1
Hi Ville,

On Mon,  2 Sep 2019 16:15:46 +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Let's make cea_db_offsets() a bit more convenient to use by
> setting the start/end offsets to zero whenever the data block
> collection isn't present. This makes it safe for the caller
> to blindly iterate the data blocks even if there are none.
> 
> Cc: Jean Delvare <jdelvare@suse.de>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_edid.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 7b3072fc550b..e5905dc764c1 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -3690,6 +3690,9 @@ cea_revision(const u8 *cea)
>  static int
>  cea_db_offsets(const u8 *cea, int *start, int *end)
>  {
> +	*start = 0;
> +	*end = 0;
> +
>  	if (cea_revision(cea) < 3)
>  		return -ENOTSUPP;
>  
> @@ -4116,10 +4119,7 @@ static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid)
>  	if (cea_revision(cea) >= 3) {
>  		int i, start, end;
>  
> -		if (cea_db_offsets(cea, &start, &end)) {
> -			start = 0;
> -			end = 0;
> -		}
> +		cea_db_offsets(cea, &start, &end);
>  
>  		for_each_cea_db(cea, i, start, end) {
>  			db = &cea[i];

Not sure if that's really needed. As it stands there's only one
function which wants to continue after cea_db_offsets() fails, all
others just bail out at that point. Now that cea_db_offsets() checks
for revision >= 3, the construct above could simply become:

	int i, start, end;

	if (cea_db_offsets(cea, &start, &end) == 0) {
		for_each_cea_db(cea, i, start, end) {
			db = &cea[i];

which is IMHO more elegant and does not require zeroing start and end
in cea_db_offsets().
Ville Syrjälä Sept. 10, 2019, 9:48 a.m. UTC | #2
On Tue, Sep 10, 2019 at 11:46:20AM +0200, Jean Delvare wrote:
> Hi Ville,
> 
> On Mon,  2 Sep 2019 16:15:46 +0300, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > Let's make cea_db_offsets() a bit more convenient to use by
> > setting the start/end offsets to zero whenever the data block
> > collection isn't present. This makes it safe for the caller
> > to blindly iterate the data blocks even if there are none.
> > 
> > Cc: Jean Delvare <jdelvare@suse.de>
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/drm_edid.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> > index 7b3072fc550b..e5905dc764c1 100644
> > --- a/drivers/gpu/drm/drm_edid.c
> > +++ b/drivers/gpu/drm/drm_edid.c
> > @@ -3690,6 +3690,9 @@ cea_revision(const u8 *cea)
> >  static int
> >  cea_db_offsets(const u8 *cea, int *start, int *end)
> >  {
> > +	*start = 0;
> > +	*end = 0;
> > +
> >  	if (cea_revision(cea) < 3)
> >  		return -ENOTSUPP;
> >  
> > @@ -4116,10 +4119,7 @@ static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid)
> >  	if (cea_revision(cea) >= 3) {
> >  		int i, start, end;
> >  
> > -		if (cea_db_offsets(cea, &start, &end)) {
> > -			start = 0;
> > -			end = 0;
> > -		}
> > +		cea_db_offsets(cea, &start, &end);
> >  
> >  		for_each_cea_db(cea, i, start, end) {
> >  			db = &cea[i];
> 
> Not sure if that's really needed. As it stands there's only one
> function which wants to continue after cea_db_offsets() fails, all
> others just bail out at that point. Now that cea_db_offsets() checks
> for revision >= 3, the construct above could simply become:
> 
> 	int i, start, end;
> 
> 	if (cea_db_offsets(cea, &start, &end) == 0) {
> 		for_each_cea_db(cea, i, start, end) {
> 			db = &cea[i];
> 
> which is IMHO more elegant and does not require zeroing start and end
> in cea_db_offsets().

I dislike indentation. Also could perhaps even move the cea_db_offsets()
into the for_each_cea_db() macro so that the caller doesn't have to care
about these mundane details at all.
Jean Delvare Sept. 10, 2019, 10:08 a.m. UTC | #3
On Tue, 10 Sep 2019 12:48:42 +0300, Ville Syrjälä wrote:
> On Tue, Sep 10, 2019 at 11:46:20AM +0200, Jean Delvare wrote:
> > Hi Ville,
> > 
> > On Mon,  2 Sep 2019 16:15:46 +0300, Ville Syrjala wrote:  
> > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > 
> > > Let's make cea_db_offsets() a bit more convenient to use by
> > > setting the start/end offsets to zero whenever the data block
> > > collection isn't present. This makes it safe for the caller
> > > to blindly iterate the data blocks even if there are none.
> > > 
> > > Cc: Jean Delvare <jdelvare@suse.de>
> > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > ---
> > >  drivers/gpu/drm/drm_edid.c | 8 ++++----
> > >  1 file changed, 4 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> > > index 7b3072fc550b..e5905dc764c1 100644
> > > --- a/drivers/gpu/drm/drm_edid.c
> > > +++ b/drivers/gpu/drm/drm_edid.c
> > > @@ -3690,6 +3690,9 @@ cea_revision(const u8 *cea)
> > >  static int
> > >  cea_db_offsets(const u8 *cea, int *start, int *end)
> > >  {
> > > +	*start = 0;
> > > +	*end = 0;
> > > +
> > >  	if (cea_revision(cea) < 3)
> > >  		return -ENOTSUPP;
> > >  
> > > @@ -4116,10 +4119,7 @@ static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid)
> > >  	if (cea_revision(cea) >= 3) {
> > >  		int i, start, end;
> > >  
> > > -		if (cea_db_offsets(cea, &start, &end)) {
> > > -			start = 0;
> > > -			end = 0;
> > > -		}
> > > +		cea_db_offsets(cea, &start, &end);
> > >  
> > >  		for_each_cea_db(cea, i, start, end) {
> > >  			db = &cea[i];  
> > 
> > Not sure if that's really needed. As it stands there's only one
> > function which wants to continue after cea_db_offsets() fails, all
> > others just bail out at that point. Now that cea_db_offsets() checks
> > for revision >= 3, the construct above could simply become:
> > 
> > 	int i, start, end;
> > 
> > 	if (cea_db_offsets(cea, &start, &end) == 0) {
> > 		for_each_cea_db(cea, i, start, end) {
> > 			db = &cea[i];
> > 
> > which is IMHO more elegant and does not require zeroing start and end
> > in cea_db_offsets().  
> 
> I dislike indentation.

It would be the same as currently, so it's not that bad. But well I'm
not maintaining that piece of code so it's not my call anyway.

> Also could perhaps even move the cea_db_offsets()
> into the for_each_cea_db() macro so that the caller doesn't have to care
> about these mundane details at all.

If the macro stays readable, why not.

Patch
diff mbox series

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 7b3072fc550b..e5905dc764c1 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -3690,6 +3690,9 @@  cea_revision(const u8 *cea)
 static int
 cea_db_offsets(const u8 *cea, int *start, int *end)
 {
+	*start = 0;
+	*end = 0;
+
 	if (cea_revision(cea) < 3)
 		return -ENOTSUPP;
 
@@ -4116,10 +4119,7 @@  static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid)
 	if (cea_revision(cea) >= 3) {
 		int i, start, end;
 
-		if (cea_db_offsets(cea, &start, &end)) {
-			start = 0;
-			end = 0;
-		}
+		cea_db_offsets(cea, &start, &end);
 
 		for_each_cea_db(cea, i, start, end) {
 			db = &cea[i];