Hi Luca, On Mon, Aug 19, 2024 at 01:38:40PM +0200, Luca Ceresoli wrote: > On Tue, 13 Aug 2024 16:32:50 +0200 > > On Tue, Aug 13, 2024 at 10:16:43AM +0200, Luca Ceresoli wrote: > > > On Thu, 8 Aug 2024 11:35:23 +0100 > > > Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx> wrote: > > > > On Thu, Aug 08, 2024 at 12:26:14PM +0200, Luca Ceresoli wrote: > > > > > When devm_drm_of_get_bridge() fails, the probe fails silently. Use > > > > > dev_err_probe() instead to log an error or report the deferral reason, > > > > > whichever is applicable. > > > > > > > > > > Signed-off-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx> > > > > > --- > > > > > drivers/gpu/drm/bridge/ti-sn65dsi83.c | 2 +- > > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > > > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c > > > > > index 57a7ed13f996..60b9f14d769a 100644 > > > > > --- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c > > > > > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c > > > > > @@ -606,7 +606,7 @@ static int sn65dsi83_parse_dt(struct sn65dsi83 *ctx, enum sn65dsi83_model model) > > > > > > > > > > panel_bridge = devm_drm_of_get_bridge(dev, dev->of_node, 2, 0); > > > > > if (IS_ERR(panel_bridge)) > > > > > - return PTR_ERR(panel_bridge); > > > > > + return dev_err_probe(dev, PTR_ERR(panel_bridge), "Failed to get panel bridge\n"); > > > > > > > > patch looks good, but the message is a bit misleading. You are > > > > not failing to get the panel bridge, but you are failing to find > > > > a panel bridge in a DT node. Right? > > > > > > As I can see from both the documentation and the code, > > > devm_drm_of_get_bridge() is really returning a pointer to a panel > > > bridge, potentially allocating and adding it in case it was not present > > > before. Navigating the device tree is only a part of what it does. > > > > > > Do you think I am missing something? > > > > No, maybe it's me being a bit pedantic. In the sense that we are > > not really failing to get the panel, but most probably the panel > > is not installed. > > The panels I'm used to, which I believe to be the most common in > embedded systems just have no way of being detected, so the operating > system cannot detect a "panel not installed" condition. > > However I went back to the code and realized your initial remark ("you > are failing to find a panel bridge in a DT node") is more correct than > I initially thought. Indeed there are two failure reasons for > devm_drm_of_get_bridge() to fail: DT lookup and panel bridge creation > failures. The latter however can be due to -ENOMEM (unlikely) or > (panel->connector_type == DRM_MODE_CONNECTOR_Unknown), which in turn > can be due to either a panel driver error or again a DT error in case > the driver gets the panel type from DT, as panel-simple.c does. > > That said, the role of devm_drm_of_get_bridge() is to provide a panel > bridge object. If it fails, that means it is unable to provide such an > object for whatever reason. Reasons currently include DT issues (the > most likely), driver bug and -ENOMEM. There could be more reasons in > future versions of the implementation. > > I'm afraid I'm unable to express all the above logic in a single commit > title line. However, should you have a better commit title or message > to suggest, I'm still open to improvements. I value good commit > messages. yes, that's all correct... I'm just assuming that we don't fail for enomem's or similar. But if you want to include them, then a generic "get" might work. To be honest, I wouldn't know how to write it better :-D Writing error messages is skill per se. Maybe something like ... "Failed to get panel bridge from DT (%pe)", panel_bridge); Fact is that an error message should immidiately tell you what is failing and you understand without browsing the code. A generic "Failed to get..." says very little. A use case can be if you receive a bug report. If someone tells you "Failed to get..." you will need to start diggin on the report. While if someone tells you "Failed to get panel bridge from DT (-ENODEV)" you would immediately tell him to add the panel in the configuration. But... as I said... > > I'm not strong on this comment, though, so that > > feel free to add: ... this is a nitpick, feel free to ignore it. > > Reviewed-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx> > > Otherwise, I'm sending v2 with your review tag by the end of the week. Thanks, Andi