pwm: Try to load modules during pwm_get()

Add a module name string to the pwm_lookup struct and if specified try
to load the module using request_module() if pwmchip_find_by_name() is
unable to find the PWM chip.

This is a last resort to work around drivers that can't - and can't be
made to - deal with deferred probe.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
[thierry.reding@gmail.com: rename new macro, reword commit message]
[thierry.reding@gmail.com: add comment explaining use-case]
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 799c4fb4cc2faeba3770f8e743798f23c3ff5563..a0860b30bd931760480ca6800d539d08d6433478 100644 (file)
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -765,6 +765,7 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id)
        unsigned int best = 0;
        struct pwm_lookup *p, *chosen = NULL;
        unsigned int match;
+       int err;
 
        /* look up via DT first */
        if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node)
@@ -825,6 +826,19 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id)
                return ERR_PTR(-ENODEV);
 
        chip = pwmchip_find_by_name(chosen->provider);
+
+       /*
+        * If the lookup entry specifies a module, load the module and retry
+        * the PWM chip lookup. This can be used to work around driver load
+        * ordering issues if driver's can't be made to properly support the
+        * deferred probe mechanism.
+        */
+       if (!chip && chosen->module) {
+               err = request_module(chosen->module);
+               if (err == 0)
+                       chip = pwmchip_find_by_name(chosen->provider);
+       }
+
        if (!chip)
                return ERR_PTR(-EPROBE_DEFER);
 

diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index eae215ef1b2cc9036db0df5cd73b60d8708418d8..08fad7c6a4713c459051779baf4bc8e909bc3377 100644 (file)
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -603,18 +603,25 @@ struct pwm_lookup {
        const char *con_id;
        unsigned int period;
        enum pwm_polarity polarity;
+       const char *module; /* optional, may be NULL */
 };
 
-#define PWM_LOOKUP(_provider, _index, _dev_id, _con_id, _period, _polarity) \
-       {                                               \
-               .provider = _provider,                  \
-               .index = _index,                        \
-               .dev_id = _dev_id,                      \
-               .con_id = _con_id,                      \
-               .period = _period,                      \
-               .polarity = _polarity                   \
+#define PWM_LOOKUP_WITH_MODULE(_provider, _index, _dev_id, _con_id,    \
+                              _period, _polarity, _module)             \
+       {                                                               \
+               .provider = _provider,                                  \
+               .index = _index,                                        \
+               .dev_id = _dev_id,                                      \
+               .con_id = _con_id,                                      \
+               .period = _period,                                      \
+               .polarity = _polarity,                                  \
+               .module = _module,                                      \
        }
 
+#define PWM_LOOKUP(_provider, _index, _dev_id, _con_id, _period, _polarity) \
+       PWM_LOOKUP_WITH_MODULE(_provider, _index, _dev_id, _con_id, _period, \
+                              _polarity, NULL)
+
 #if IS_ENABLED(CONFIG_PWM)
 void pwm_add_table(struct pwm_lookup *table, size_t num);
 void pwm_remove_table(struct pwm_lookup *table, size_t num);