On 2019-04-16 6:16 p.m., Lyude Paul wrote:
> Sorry for the slow response, I've been really busy ;_;
No worries :)
>
> On Fri, 2019-04-12 at 12:05 -0400, sunpeng.li@xxxxxxx wrote:
>> From: Leo Li <sunpeng.li@xxxxxxx>
>>
>> In preparation for adding aux devices for DP MST:
>>
>> 1. A non-cyclic idr is used for the device minor version. That way,
>> hotplug cycling MST devices won't needlessly increment the minor
>> version index.
>
> I really like this btw, cyclic idrs are really annoying for drm_dp_aux_dev,
> even outside of MST (try reloading a drm driver a couple of times and you'll
> understand ;). I think we should split this into another commit though
>
>> 2. A suffix option is added to the aux device file name. It can be used
>> to identify the corresponding MST device.
>
> I like this idea, but I think there may be a better way that we can do this.
> Using /dev/nvme* as an example, we have the standard dev paths (/dev/nvme0,
> /dev/nvme0n1, etc.). But we can also access them through /dev/disk/by-
> {id,label,partlabel,partuuid,path,uuid}.
>
> So what if we added something similar for aux devices? We start off with the
> standard /dev/drm_dp_aux*, then provide more descriptive symlinks and
> directories:
>
> (feel free to come up with better naming then this if you can)
>
> /dev/drm_dp_aux/card0-DP-1 -> /dev/drm_dp_aux1
> /dev/drm_dp_aux/card0-DP-2 -> /dev/drm_dp_aux2
> etc.
That does sound neater - although FWICT, this will have to be done with
udev rules?
I took a brief look at how that's done for storage devices. It looks
like they have rules defined in
/lib/udev/rules.d/60-persistent-storage.rules that manages the "by-x"
symlinks.
To make this happen for aux devices, what we could do is attach sysfs
attributes to the device. It can then be parsed by udev in a similar
fashion. Currently, only 'name' attribute is attached, as seen in
drm_dp_aux_dev.c (after name_show()).
Thanks,
Leo
>
>>
>> Signed-off-by: Leo Li <sunpeng.li@xxxxxxx>
>> ---
>> drivers/gpu/drm/drm_crtc_helper_internal.h | 5 +++--
>> drivers/gpu/drm/drm_dp_aux_dev.c | 8 ++++----
>> drivers/gpu/drm/drm_dp_helper.c | 2 +-
>> 3 files changed, 8 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_crtc_helper_internal.h
>> b/drivers/gpu/drm/drm_crtc_helper_internal.h
>> index b5ac158..9f0907b 100644
>> --- a/drivers/gpu/drm/drm_crtc_helper_internal.h
>> +++ b/drivers/gpu/drm/drm_crtc_helper_internal.h
>> @@ -46,7 +46,7 @@ static inline int drm_fb_helper_modinit(void)
>> #ifdef CONFIG_DRM_DP_AUX_CHARDEV
>> int drm_dp_aux_dev_init(void);
>> void drm_dp_aux_dev_exit(void);
>> -int drm_dp_aux_register_devnode(struct drm_dp_aux *aux);
>> +int drm_dp_aux_register_devnode(struct drm_dp_aux *aux, const char
>> *suffix);
>> void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux);
>> #else
>> static inline int drm_dp_aux_dev_init(void)
>> @@ -58,7 +58,8 @@ static inline void drm_dp_aux_dev_exit(void)
>> {
>> }
>>
>> -static inline int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
>> +static inline int drm_dp_aux_register_devnode(struct drm_dp_aux *aux,
>> + const char *suffix)
>> {
>> return 0;
>> }
>> diff --git a/drivers/gpu/drm/drm_dp_aux_dev.c
>> b/drivers/gpu/drm/drm_dp_aux_dev.c
>> index 0e4f25d..2310a67 100644
>> --- a/drivers/gpu/drm/drm_dp_aux_dev.c
>> +++ b/drivers/gpu/drm/drm_dp_aux_dev.c
>> @@ -80,8 +80,7 @@ static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct
>> drm_dp_aux *aux)
>> kref_init(&aux_dev->refcount);
>>
>> mutex_lock(&aux_idr_mutex);
>> - index = idr_alloc_cyclic(&aux_idr, aux_dev, 0, DRM_AUX_MINORS,
>> - GFP_KERNEL);
>> + index = idr_alloc(&aux_idr, aux_dev, 0, DRM_AUX_MINORS, GFP_KERNEL);
>> mutex_unlock(&aux_idr_mutex);
>> if (index < 0) {
>> kfree(aux_dev);
>> @@ -290,7 +289,7 @@ void drm_dp_aux_unregister_devnode(struct drm_dp_aux
>> *aux)
>> kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
>> }
>>
>> -int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
>> +int drm_dp_aux_register_devnode(struct drm_dp_aux *aux, const char *suffix)
>> {
>> struct drm_dp_aux_dev *aux_dev;
>> int res;
>> @@ -301,7 +300,8 @@ int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
>>
>> aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
>> MKDEV(drm_dev_major, aux_dev->index),
>> NULL,
>> - "drm_dp_aux%d", aux_dev->index);
>> + "drm_dp_aux%d%s", aux_dev->index,
>> + suffix ? suffix : "");
>> if (IS_ERR(aux_dev->dev)) {
>> res = PTR_ERR(aux_dev->dev);
>> aux_dev->dev = NULL;
>> diff --git a/drivers/gpu/drm/drm_dp_helper.c
>> b/drivers/gpu/drm/drm_dp_helper.c
>> index e2266ac..13f1005 100644
>> --- a/drivers/gpu/drm/drm_dp_helper.c
>> +++ b/drivers/gpu/drm/drm_dp_helper.c
>> @@ -1143,7 +1143,7 @@ int drm_dp_aux_register(struct drm_dp_aux *aux)
>> strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(aux->dev),
>> sizeof(aux->ddc.name));
>>
>> - ret = drm_dp_aux_register_devnode(aux);
>> + ret = drm_dp_aux_register_devnode(aux, NULL);
>> if (ret)
>> return ret;
>>
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