Messages in this thread | | | Date | Wed, 31 Mar 2021 20:04:35 +0200 | From | Greg KH <> | Subject | Re: [PATCH v5 2/5] powercap/drivers/dtpm: Create a registering system |
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On Wed, Mar 31, 2021 at 01:00:45PM +0200, Daniel Lezcano wrote: > A SoC can be differently structured depending on the platform and the > kernel can not be aware of all the combinations, as well as the > specific tweaks for a particular board. > > The creation of the hierarchy must be delegated to userspace.
Isn't that what DT is for?
> These changes provide a registering mechanism where the different > subsystems will initialize their dtpm backends and register with a > name the dtpm node in a list. > > The next changes will provide an userspace interface to create > hierarchically the different nodes. Those will be created by name and > found via the list filled by the different subsystem. > > If a specified name is not found in the list, it is assumed to be a > virtual node which will have children and the default is to allocate > such node.
There's no userspace portion here, so why talk about it?
> > Cc: Greg KH <gregkh@linuxfoundation.org> > Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> > Reviewed-by: Lukasz Luba <lukasz.luba@arm.com> > --- > > V5: > - Decrease log level from 'info' to 'debug' > - Remove the refcount, it is pointless, lifetime cycle is already > handled by the device refcounting. The dtpm node allocator is in > charge of freeing it. > - Rename the functions to 'dtpm_add, dtpm_del, dtpm_lookup' > - Fix missing kfrees when deleting the node from the list > V4: > - Fixed typo in the commit log > V2: > - Fixed error code path by dropping lock > --- > drivers/powercap/dtpm.c | 121 ++++++++++++++++++++++++++++++++++-- > drivers/powercap/dtpm_cpu.c | 8 +-- > include/linux/dtpm.h | 6 ++ > 3 files changed, 127 insertions(+), 8 deletions(-) > > diff --git a/drivers/powercap/dtpm.c b/drivers/powercap/dtpm.c > index 58433b8ef9a1..8df7adeed0cf 100644 > --- a/drivers/powercap/dtpm.c > +++ b/drivers/powercap/dtpm.c > @@ -34,6 +34,14 @@ static DEFINE_MUTEX(dtpm_lock); > static struct powercap_control_type *pct; > static struct dtpm *root; > > +struct dtpm_node { > + const char *name; > + struct dtpm *dtpm; > + struct list_head node; > +}; > + > +static LIST_HEAD(dtpm_list); > + > static int get_time_window_us(struct powercap_zone *pcz, int cid, u64 *window) > { > return -ENOSYS; > @@ -152,6 +160,113 @@ static int __dtpm_update_power(struct dtpm *dtpm) > return ret; > } > > +static struct dtpm *__dtpm_lookup(const char *name) > +{ > + struct dtpm_node *node; > + > + list_for_each_entry(node, &dtpm_list, node) { > + if (!strcmp(name, node->name)) > + return node->dtpm; > + } > + > + return NULL; > +} > + > +/** > + * dtpm_lookup - Lookup for a registered dtpm node given its name > + * @name: the name of the dtpm device > + * > + * The function looks up in the list of the registered dtpm > + * devices. This function must be called to create a dtpm node in the > + * powercap hierarchy. > + * > + * Return: a pointer to a dtpm structure, NULL if not found. > + */ > +struct dtpm *dtpm_lookup(const char *name) > +{ > + struct dtpm *dtpm; > + > + mutex_lock(&dtpm_lock); > + dtpm = __dtpm_lookup(name); > + mutex_unlock(&dtpm_lock); > + > + return dtpm; > +} > + > +/** > + * dtpm_add - Add the dtpm in the dtpm list > + * @name: a name used as an identifier > + * @dtpm: the dtpm node to be registered > + * > + * Stores the dtpm device in a list. The list contains all the devices > + * which are power capable in terms of limitation and power > + * consumption measurements. Even if conceptually, a power capable > + * device won't register itself twice, the function will check if it > + * was already registered in order to prevent a misuse of the API. > + * > + * Return: 0 on success, -EEXIST if the device name is already present > + * in the list, -ENOMEM in case of memory allocation failure. > + */ > +int dtpm_add(const char *name, struct dtpm *dtpm)
Why not just use the name of the dtpm?
Where does this "new" name come from? And why would it differ?
> +{ > + struct dtpm_node *node; > + int ret; > + > + mutex_lock(&dtpm_lock); > + > + ret = -EEXIST; > + if (__dtpm_lookup(name)) > + goto out_unlock;
Why do you have yet-another-list of these devices? They are already all on a list, why do you need another?
And you seem to be ignoring reference count issues here, you add a reference counted pointer to a random list in the kernel and never increment the reference count. That's bad :(
So just don't use a new list please...
thanks,
greg k-h
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