Re: [Qemu-devel] [PATCH 1/2] device_tree: Add qemu_devtree_setprop_sized_cells() utility function

[Alexander Graf]

On 24.06.2013, at 12:22, Peter Maydell wrote:

> We already have a qemu_devtree_setprop_cells() which sets a dtb
> property to an array of cells whose values are specified by varargs.
> However for the fairly common case of setting a property to a list
> of addresses or of address,size pairs the number of cells used by
> each element in the list depends on the parent's #address-cells
> and #size-cells properties. To make this easier we provide an analogous
> qemu_devtree_setprop_sized_cells() function which allows the number
> of cells used by each element to be specified.
> 
> Signed-off-by: Peter Maydell <address@hidden>

This looks pretty complicated for something actually quite simple: All you want 
is to pass in a number of 64bit values, rather than 32bit ones, right? There's 
got to be an easier way to implement that.


Alex

> ---
> device_tree.c                |   48 ++++++++++++++++++++++++++++++++++++++++++
> include/sysemu/device_tree.h |   29 +++++++++++++++++++++++++
> 2 files changed, 77 insertions(+)
> 
> diff --git a/device_tree.c b/device_tree.c
> index 69be9da..15a081c 100644
> --- a/device_tree.c
> +++ b/device_tree.c
> @@ -319,3 +319,51 @@ void qemu_devtree_dumpdtb(void *fdt, int size)
>     }
> 
> }
> +
> +int qemu_devtree_setprop_sized_cells(void *fdt, const char *node_path,
> +                                     const char *property, ...)
> +{
> +    uint32_t *propcells;
> +    uint32_t propsize = 0;
> +    va_list ap;
> +    uint32_t ncells;
> +    uint64_t value;
> +    int i, argnum;
> +
> +    va_start(ap, property);
> +    for (;;) {
> +        ncells = va_arg(ap, uint32_t);
> +        if (!ncells) {
> +            break;
> +        }
> +        assert(ncells < 3);
> +        propsize += ncells;
> +        value = va_arg(ap, uint64_t);
> +    }
> +    va_end(ap);
> +
> +    propcells = g_new0(uint32_t, propsize);
> +
> +    i = 0;
> +    va_start(ap, property);
> +    for (argnum = 1; ; argnum++) {
> +        uint32_t hival;
> +
> +        ncells = va_arg(ap, uint32_t);
> +        if (!ncells) {
> +            break;
> +        }
> +        value = va_arg(ap, uint64_t);
> +        hival = cpu_to_be32(value >> 32);
> +        if (ncells > 1) {
> +            propcells[i++] = hival;
> +        } else if (hival != 0) {
> +            return argnum;
> +        }
> +        propcells[i++] = cpu_to_be32(value);
> +    }
> +    va_end(ap);
> +
> +    return qemu_devtree_setprop(fdt, node_path, property, propcells,
> +                                propsize * sizeof(uint32_t));
> +}
> diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h
> index f0b3f35..d7691f9 100644
> --- a/include/sysemu/device_tree.h
> +++ b/include/sysemu/device_tree.h
> @@ -51,4 +51,33 @@ int qemu_devtree_add_subnode(void *fdt, const char *name);
> 
> void qemu_devtree_dumpdtb(void *fdt, int size);
> 
> +/**
> + * qemu_devtree_setprop_sized_cells:
> + * @fdt: device tree blob
> + * @node_path: node to set property on
> + * @property: property to set
> + * @...: 0-terminated list of uint32_t number-of-cells, uint64_t value pairs
> + *
> + * Set the specified property on the specified node in the device tree
> + * to be an array of cells. The values of the cells are specified via
> + * the varargs list, which alternates between "number of cells used by
> + * this value" and "value" (terminated when number-of-cells is zero).
> + * number-of-cells must be either 1 or 2 (other values will assert()).
> + *
> + * This function is useful because device tree nodes often have cell arrays
> + * which are either lists of addresses or lists of address,size tuples, but
> + * the number of cells used for each element vary depending on the
> + * #address-cells and #size-cells properties of their parent node.
> + * If you know all your cell elements are one cell wide you can use the
> + * simpler qemu_devtree_setprop_cells().
> + *
> + * Return value: 0 on success, <0 if setting the property failed,
> + * n (for n>0) if value n wouldn't fit in the required number of cells.
> + * (This slightly odd convention is for the benefit of callers who might
> + * wish to print different error messages depending on which value
> + * was too large to fit, since values might be user-specified.)
> + */
> +int qemu_devtree_setprop_sized_cells(void *fdt, const char *node_path,
> +                                     const char *property, ...);
> +
> #endif /* __DEVICE_TREE_H__ */
> -- 
> 1.7.9.5
>