Re: [Minios-devel] [UNIKRAFT PATCH RFC v2 1/7] plat/drivers/ofw: Introduce fdt_get_last_node_by_compatible

[Santiago Pagani <Santiago.Pagani@xxxxxxxxx>]

Hi Justin,

Thanks fort he patch. Please see my comments inline.

Best,
Santiago

On 23.10.19, 05:52, "Minios-devel on behalf of Jia He" 
<minios-devel-bounces@xxxxxxxxxxxxxxxxxxxx on behalf of justin.he@xxxxxxx> 
wrote:

    This patch provides a helper for fdt to get the last node in dts
    by the name of compatible matching
    
    Signed-off-by: Jia He <justin.he@xxxxxxx>
    ---
     plat/drivers/include/ofw/fdt.h | 20 ++++++++++++++++++++
     plat/drivers/ofw/fdt.c         | 27 +++++++++++++++++++++++++++
     2 files changed, 47 insertions(+)
    
    diff --git a/plat/drivers/include/ofw/fdt.h b/plat/drivers/include/ofw/fdt.h
    index 6f80a27..b2fb27d 100644
    --- a/plat/drivers/include/ofw/fdt.h
    +++ b/plat/drivers/include/ofw/fdt.h
    @@ -137,4 +137,24 @@ int fdt_node_offset_by_compatible_list(const void 
*fdt, int startoffset,
      */
     int fdt_get_interrupt(const void *fdt, int nodeoffset,
                                uint32_t index, int *size, fdt32_t **prop);
    +
    +/**
    + * fdt_get_last_node_by_compatible - get the last compatible node in fdt
    + * @fdt: pointer to the device tree blob
    + * @endoffset: end offset of the node to find the address for
    + * @compatibles: a list of 'compatible' string to match, should be ended
    + * with NULL string.
    + * If endoffset is -1, no limitation
    + * Else try to get he last node by compatible between [0, endoffset)
    + * returns:
    + *     0 on success , < 0 on failed > 0 the found offset
The comment explaining the return value could be better explained. The way it 
reads is that 0 means success, less than 0 is an error, and larger than zero is 
the found offset. However, 0 is probably a valid offset to return, and any 
other value returned as offset is also valid. Therefore, it should read 
something like: ">= 0 on success (where the value is the found offset), < 0 on 
failure:", and then like you have now the possible error codes.
    + * -FDT_ERR_NOTFOUND, if the given node has no 'compatible' property
    + * -FDT_ERR_BADOFFSET, if nodeoffset does not refer to a BEGIN_NODE tag
    + * -FDT_ERR_BADMAGIC,
    + * -FDT_ERR_BADVERSION,
    + * -FDT_ERR_BADSTATE,
    + * -FDT_ERR_BADSTRUCTURE, standard meanings
    + */
    +int fdt_get_last_node_by_compatible(const void *fdt, int endoffset,
    +                               const char * const compatible);
     #endif
    diff --git a/plat/drivers/ofw/fdt.c b/plat/drivers/ofw/fdt.c
    index 76f8ff3..a8fe18f 100644
    --- a/plat/drivers/ofw/fdt.c
    +++ b/plat/drivers/ofw/fdt.c
    @@ -288,3 +288,30 @@ int fdt_get_interrupt(const void *fdt, int nodeoffset,
     
        return 0;
     }
    +
    +/*
    + * get the last compatible node in fdt
    + * If endoffset is -1, no limitation
    + * Else try to get he last node by compatible between [0, endoffset)
    + */
    +int fdt_get_last_node_by_compatible(const void *fdt, int endoffset,
    +                               const char * const compatible)
    +{
    +   int offset, err;
    +   int lastoffset = -FDT_ERR_NOTFOUND;
    +
    +   for (offset = fdt_next_node(fdt, -1, NULL); offset >= 0;
    +                           offset = fdt_next_node(fdt, offset, NULL)) {
    +           err = fdt_node_check_compatible(fdt, offset, compatible);
    +           if ((err < 0) && (err != -FDT_ERR_NOTFOUND))
    +                   return err;
    +           else if (err == 0) /* found */ {
    +                   if (endoffset != -1 && offset >= endoffset)
    +                           return lastoffset;
    +
    +                   lastoffset = offset;
    +           }
    +   }
    +
    +   return lastoffset; /* last node offset */
    +}
    -- 
    2.17.1
    
    
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