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From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     "Rafael J. Wysocki" <rafael@kernel.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Len Brown <lenb@kernel.org>,
        Calvin Johnson <calvin.johnson@oss.nxp.com>
Subject: Re: [PATCH v1 7/7] ACPI: property: Allow counting a single value as an array of 1 element
Date:   Wed, 10 Feb 2021 14:48:09 +0100
Message-ID: <1946478.1QpZic6vku@kreacher>
In-Reply-To: <3881654.NPl3a4M0kB@kreacher>
References: <20210210114320.3478-1-andriy.shevchenko@linux.intel.com> <CAJZ5v0hx78JHnP5-5xFTPr0Rh9FvPCzAzTCyBaT6eLZ3Dd-mFA@mail.gmail.com> <3881654.NPl3a4M0kB@kreacher>
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On Wednesday, February 10, 2021 2:31:48 PM CET Rafael J. Wysocki wrote:
> On Wednesday, February 10, 2021 1:36:00 PM CET Rafael J. Wysocki wrote:
> > On Wed, Feb 10, 2021 at 12:51 PM Andy Shevchenko
> > <andriy.shevchenko@linux.intel.com> wrote:
> > >
> > > We allow to read the single value as a first element in the array.
> > > Unfortunately the counting doesn't work in this case and we can't
> > > call fwnode_property_count_*() API without getting an error.
> > 
> > It would be good to mention what the symptom of the issue is here.
> > 
> > > Modify acpi_data_prop_read() to always try the single value read
> > > and thus allow counting the single value as an array of 1 element.
> > >
> > > Reported-by: Calvin Johnson <calvin.johnson@oss.nxp.com>
> > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > 
> > This is a bug fix, so it should go in before the cleanups in this series IMO.
> > 
> > Also it looks like stable@vger material.
> > 
> > > ---
> > >  drivers/acpi/property.c | 6 ++++--
> > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
> > > index 236316ee0e25..d6100585fceb 100644
> > > --- a/drivers/acpi/property.c
> > > +++ b/drivers/acpi/property.c
> > > @@ -913,12 +913,14 @@ static int acpi_data_prop_read(const struct acpi_device_data *data,
> > >         const union acpi_object *items;
> > >         int ret;
> > >
> > > -       if (val && nval == 1) {
> > > +       /* Try to read as a single value first */
> > > +       if (!val || nval == 1) {
> > >                 ret = acpi_data_prop_read_single(data, propname, proptype, val);
> > 
> > This returns -EINVAL if val is NULL.
> > 
> > >                 if (ret >= 0)
> > > -                       return ret;
> > > +                       return val ? ret : 1;
> > 
> > So val cannot be NULL here.
> > 
> > >         }
> > >
> > > +       /* It's not the single value, get an array instead */
> > >         ret = acpi_data_get_property_array(data, propname, ACPI_TYPE_ANY, &obj);
> > >         if (ret)
> > >                 return ret;
> > > --
> > 
> > To me, acpi_fwnode_property_read_string_array() needs to special-case
> > val == NULL and nval == 0.
> 
> Well, scratch this.
> 
> Something like the patch below (untested) should be sufficient to address this
> if I'm not mistaken.

Well, I am mistaken ->

> 
> ---
>  drivers/acpi/property.c |   17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
> 
> Index: linux-pm/drivers/acpi/property.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/property.c
> +++ linux-pm/drivers/acpi/property.c
> @@ -787,14 +787,14 @@ static int acpi_data_prop_read_single(co
>  	const union acpi_object *obj;
>  	int ret;
>  
> -	if (!val)
> -		return -EINVAL;
> -
>  	if (proptype >= DEV_PROP_U8 && proptype <= DEV_PROP_U64) {
>  		ret = acpi_data_get_property(data, propname, ACPI_TYPE_INTEGER, &obj);
>  		if (ret)
>  			return ret;
>  
> +		if (!val)
> +			return 1;
> +
>  		switch (proptype) {
>  		case DEV_PROP_U8:
>  			if (obj->integer.value > U8_MAX)
> @@ -820,7 +820,8 @@ static int acpi_data_prop_read_single(co
>  		if (ret)
>  			return ret;
>  
> -		*(char **)val = obj->string.pointer;
> +		if (val)
> +			*(char **)val = obj->string.pointer;
>  
>  		return 1;
>  	} else {
> @@ -928,10 +929,16 @@ static int acpi_data_prop_read(const str
>  	const union acpi_object *items;
>  	int ret;
>  
> -	if (val && nval == 1) {
> +	if (nval == 1) {

-> because this would miss the nval == 0 case.

So appended again with this fixed.

---
 drivers/acpi/property.c |   17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

Index: linux-pm/drivers/acpi/property.c
===================================================================
--- linux-pm.orig/drivers/acpi/property.c
+++ linux-pm/drivers/acpi/property.c
@@ -787,14 +787,14 @@ static int acpi_data_prop_read_single(co
 	const union acpi_object *obj;
 	int ret;
 
-	if (!val)
-		return -EINVAL;
-
 	if (proptype >= DEV_PROP_U8 && proptype <= DEV_PROP_U64) {
 		ret = acpi_data_get_property(data, propname, ACPI_TYPE_INTEGER, &obj);
 		if (ret)
 			return ret;
 
+		if (!val)
+			return 1;
+
 		switch (proptype) {
 		case DEV_PROP_U8:
 			if (obj->integer.value > U8_MAX)
@@ -820,7 +820,8 @@ static int acpi_data_prop_read_single(co
 		if (ret)
 			return ret;
 
-		*(char **)val = obj->string.pointer;
+		if (val)
+			*(char **)val = obj->string.pointer;
 
 		return 1;
 	} else {
@@ -928,10 +929,16 @@ static int acpi_data_prop_read(const str
 	const union acpi_object *items;
 	int ret;
 
-	if (val && nval == 1) {
+	if (nval <= 1) {
 		ret = acpi_data_prop_read_single(data, propname, proptype, val);
 		if (ret >= 0)
 			return ret;
+
+		/*
+		 * Reading this property as a single-value one failed, but its
+		 * value may still be represented as one-element array, so
+		 * continue.
+		 */
 	}
 
 	ret = acpi_data_get_property_array(data, propname, ACPI_TYPE_ANY, &obj);