Re: [PATCH v3 06/17] xen/device-tree: Add dt_property_read_variable_u32_array helper

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Rahul,

> On 28 Sep 2021, at 19:18, Rahul Singh <rahul.singh@xxxxxxx> wrote:
> 
> Based Linux commit a67e9472da423ec47a3586920b526ebaedf25fc3
> 
> Import the Linux helper of_property_read_variable_u32_array. This
> function find and read an array of 32 bit integers from a property,
> with bounds on the minimum and maximum array size.
> 
> Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Cheers
Bertrand

> ---
> Change in v3:
> - Modify commit message to include upstream Linux commit-id not stable 
>  Linux commit-id
> Change in v2: Patch introduced in v2
> ---
> xen/common/device_tree.c      | 61 +++++++++++++++++++++++++++++++++++
> xen/include/xen/device_tree.h | 26 +++++++++++++++
> 2 files changed, 87 insertions(+)
> 
> diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
> index 03d25a81ce..53160d61f8 100644
> --- a/xen/common/device_tree.c
> +++ b/xen/common/device_tree.c
> @@ -208,6 +208,67 @@ int dt_property_read_string(const struct dt_device_node 
> *np,
>     return 0;
> }
> 
> +/**
> + * dt_find_property_value_of_size
> + *
> + * @np:     device node from which the property value is to be read.
> + * @propname:   name of the property to be searched.
> + * @min:    minimum allowed length of property value
> + * @max:    maximum allowed length of property value (0 means unlimited)
> + * @len:    if !=NULL, actual length is written to here
> + *
> + * Search for a property in a device node and valid the requested size.
> + *
> + * Return: The property value on success, -EINVAL if the property does not
> + * exist, -ENODATA if property does not have a value, and -EOVERFLOW if the
> + * property data is too small or too large.
> + */
> +static void *dt_find_property_value_of_size(const struct dt_device_node *np,
> +                                            const char *propname, u32 min,
> +                                            u32 max, size_t *len)
> +{
> +    const struct dt_property *prop = dt_find_property(np, propname, NULL);
> +
> +    if ( !prop )
> +        return ERR_PTR(-EINVAL);
> +    if ( !prop->value )
> +        return ERR_PTR(-ENODATA);
> +    if ( prop->length < min )
> +        return ERR_PTR(-EOVERFLOW);
> +    if ( max && prop->length > max )
> +        return ERR_PTR(-EOVERFLOW);
> +
> +    if ( len )
> +        *len = prop->length;
> +
> +    return prop->value;
> +}
> +
> +int dt_property_read_variable_u32_array(const struct dt_device_node *np,
> +                                        const char *propname, u32 
> *out_values,
> +                                        size_t sz_min, size_t sz_max)
> +{
> +    size_t sz, count;
> +    const __be32 *val = dt_find_property_value_of_size(np, propname,
> +                        (sz_min * sizeof(*out_values)),
> +                        (sz_max * sizeof(*out_values)),
> +                        &sz);
> +
> +    if ( IS_ERR(val) )
> +        return PTR_ERR(val);
> +
> +    if ( !sz_max )
> +        sz = sz_min;
> +    else
> +        sz /= sizeof(*out_values);
> +
> +    count = sz;
> +    while ( count-- )
> +        *out_values++ = be32_to_cpup(val++);
> +
> +    return sz;
> +}
> +
> int dt_property_match_string(const struct dt_device_node *np,
>                              const char *propname, const char *string)
> {
> diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
> index b02696be94..1693fb8e8c 100644
> --- a/xen/include/xen/device_tree.h
> +++ b/xen/include/xen/device_tree.h
> @@ -366,6 +366,32 @@ bool_t dt_property_read_u32(const struct dt_device_node 
> *np,
> bool_t dt_property_read_u64(const struct dt_device_node *np,
>                             const char *name, u64 *out_value);
> 
> +
> +/**
> + * dt_property_read_variable_u32_array - Find and read an array of 32 bit
> + * integers from a property, with bounds on the minimum and maximum array 
> size.
> + *
> + * @np:     device node from which the property value is to be read.
> + * @propname:   name of the property to be searched.
> + * @out_values: pointer to return found values.
> + * @sz_min: minimum number of array elements to read
> + * @sz_max: maximum number of array elements to read, if zero there is no
> + *      upper limit on the number of elements in the dts entry but only
> + *      sz_min will be read.
> + *
> + * Search for a property in a device node and read 32-bit value(s) from
> + * it.
> + *
> + * Return: The number of elements read on success, -EINVAL if the property
> + * does not exist, -ENODATA if property does not have a value, and -EOVERFLOW
> + * if the property data is smaller than sz_min or longer than sz_max.
> + *
> + * The out_values is modified only if a valid u32 value can be decoded.
> + */
> +int dt_property_read_variable_u32_array(const struct dt_device_node *np,
> +                                        const char *propname, u32 
> *out_values,
> +                                        size_t sz_min, size_t sz_max);
> +
> /**
>  * dt_property_read_bool - Check if a property exists
>  * @np: node to get the value
> -- 
> 2.17.1
>