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Date: Wed, 19 Feb 2014 08:54:57 -0600
From: Rob Herring <robherring2@...il.com>
To: Grant Likely <grant.likely@...aro.org>
Cc: "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Kevin Hao <haokexin@...il.com>,
Rob Herring <robh+dt@...nel.org>,
Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH v4 2/4] of: reimplement the matching method for __of_match_node()
On Wed, Feb 19, 2014 at 8:14 AM, Grant Likely <grant.likely@...aro.org> wrote:
> From: Kevin Hao <haokexin@...il.com>
>
> In the current implementation of __of_match_node(), it will compare
> each given match entry against all the node's compatible strings
> with of_device_is_compatible().
>
> To achieve multiple compatible strings per node with ordering from
> specific to generic, this requires given matches to be ordered from
> specific to generic. For most of the drivers this is not true and
> also an alphabetical ordering is more sane there.
>
> Therefore, we define a following priority order for the match, and
> then scan all the entries to find the best match.
> 1. specific compatible && type && name
> 2. specific compatible && type
> 3. specific compatible && name
> 4. specific compatible
> 5. general compatible && type && name
> 6. general compatible && type
> 7. general compatible && name
> 8. general compatible
> 9. type && name
> 10. type
> 11. name
While I agree this should be the right order, I worry that this may be
changing the matching in some case as all previous attempts have done.
>
> v4: Short-circuit failure cases instead of mucking with score, and
> remove extra __of_device_is_compatible() wrapper stub.
> Move scoring logic directly into __of_device_is_compatible()
>
> v3: Also need to bail out when there does have a compatible member in match
> entry, but it doesn't match with the device node's compatible.
>
> v2: Fix the bug such as we get the same score for the following two match
> entries with the empty node 'name2 { };'
> struct of_device_id matches[] = {
> {.name = "name2", },
> {.name = "name2", .type = "type1", },
> {}
> };
>
> Signed-off-by: Kevin Hao <haokexin@...il.com>
> [grant.likely: added v4 changes]
> Signed-off-by: Grant Likely <grant.likely@...aro.org>
> ---
> drivers/of/base.c | 108 +++++++++++++++++++++++++++++++++++++-----------------
> 1 file changed, 74 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index ba195fbce4c6..30ffc291d0a0 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -342,27 +342,73 @@ struct device_node *of_get_cpu_node(int cpu, unsigned int *thread)
> }
> EXPORT_SYMBOL(of_get_cpu_node);
>
> -/** Checks if the given "compat" string matches one of the strings in
> - * the device's "compatible" property
> +/**
> + * __of_device_is_compatible() - Check if the node matches given constraints
> + * @device: pointer to node
> + * @compat: required compatible string, NULL or "" for any match
> + * @type: required device_type value, NULL or "" for any match
> + * @name: required node name, NULL or "" for any match
> + *
> + * Checks if the given @compat, @type and @name strings match the
> + * properties of the given @device. A constraints can be skipped by
> + * passing NULL or an empty string as the constraint.
> + *
> + * Returns 0 for no match, and a positive integer on match. The return
> + * value is a relative score with larger values indicating better
> + * matches. The score is weighted for the most specific compatible value
> + * to get the highest score. Matching type is next, followed by matching
> + * name. Practically speaking, this results in the following priority
> + * order for matches:
> + *
> + * 1. specific compatible && type && name
> + * 2. specific compatible && type
> + * 3. specific compatible && name
> + * 4. specific compatible
> + * 5. general compatible && type && name
> + * 6. general compatible && type
> + * 7. general compatible && name
> + * 8. general compatible
> + * 9. type && name
> + * 10. type
> + * 11. name
> */
> static int __of_device_is_compatible(const struct device_node *device,
> - const char *compat)
> + const char *compat, const char *type, const char *name)
> {
> const char* cp;
> - int cplen, l;
> + int cplen, l, index, score = 0;
>
> - cp = __of_get_property(device, "compatible", &cplen);
> - if (cp == NULL)
> - return 0;
> - while (cplen > 0) {
> - if (of_compat_cmp(cp, compat, strlen(compat)) == 0)
> - return 1;
> - l = strlen(cp) + 1;
> - cp += l;
> - cplen -= l;
> + /* Compatible match has highest priority */
> + if (compat && compat[0]) {
> + cp = __of_get_property(device, "compatible", &cplen);
> + if (!cp)
> + return 0;
> + for (index = 0; cplen > 0; index++, cp += l, cplen -= l) {
> + l = strlen(cp) + 1;
This could use of_property_for_each_string.
> + if (of_compat_cmp(cp, compat, strlen(compat)) == 0) {
> + score = INT_MAX/2 - (index << 2);
> + break;
> + }
> + }
> + if (!score)
> + return 0;
> }
>
> - return 0;
> + /* Matching type is better than matching name */
> + if (type && type[0]) {
> + if (!device->type || of_node_cmp(type, device->type))
> + return 0;
> + score += 2;
> + }
> +
> + /* Matching name is a bit better than not */
> + if (name && name[0]) {
> + if (!device->name || of_node_cmp(name, device->name))
> + return 0;
> + score++;
> + }
> +
> + return score;
> }
>
> /** Checks if the given "compat" string matches one of the strings in
> @@ -375,7 +421,7 @@ int of_device_is_compatible(const struct device_node *device,
> int res;
>
> raw_spin_lock_irqsave(&devtree_lock, flags);
> - res = __of_device_is_compatible(device, compat);
> + res = __of_device_is_compatible(device, compat, NULL, NULL);
> raw_spin_unlock_irqrestore(&devtree_lock, flags);
> return res;
> }
> @@ -681,10 +727,7 @@ struct device_node *of_find_compatible_node(struct device_node *from,
> raw_spin_lock_irqsave(&devtree_lock, flags);
> np = from ? from->allnext : of_allnodes;
> for (; np; np = np->allnext) {
> - if (type
> - && !(np->type && (of_node_cmp(np->type, type) == 0)))
> - continue;
> - if (__of_device_is_compatible(np, compatible) &&
> + if (__of_device_is_compatible(np, compatible, type, NULL) &&
> of_node_get(np))
> break;
> }
> @@ -734,25 +777,22 @@ static
> const struct of_device_id *__of_match_node(const struct of_device_id *matches,
> const struct device_node *node)
> {
> + const struct of_device_id *best_match = NULL;
> + int score, best_score = 0;
> +
> if (!matches)
> return NULL;
>
> - while (matches->name[0] || matches->type[0] || matches->compatible[0]) {
> - int match = 1;
> - if (matches->name[0])
> - match &= node->name
> - && !strcmp(matches->name, node->name);
> - if (matches->type[0])
> - match &= node->type
> - && !strcmp(matches->type, node->type);
> - if (matches->compatible[0])
> - match &= __of_device_is_compatible(node,
> - matches->compatible);
> - if (match)
> - return matches;
> - matches++;
> + for (; matches->name[0] || matches->type[0] || matches->compatible[0]; matches++) {
> + score = __of_device_is_compatible(node, matches->compatible,
> + matches->type, matches->name);
> + if (score > best_score) {
> + best_match = matches;
> + best_score = score;
> + }
> }
> - return NULL;
> +
> + return best_match;
> }
>
> /**
> --
> 1.8.3.2
>
--
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