[Intel-gfx] [PATCH v7 1/2] drm/dp: Add a drm_aux-dev module for reading/writing dpcd registers.

[Rafael Antognolli]

This module is heavily based on i2c-dev. Once loaded, it provides one
dev node per DP AUX channel, named drm_dp_auxN, where N is an integer.

It's possible to know which connector owns this aux channel by looking
at the respective sysfs /sys/class/drm_aux_dev/drm_dp_auxN/connector, if
the connector device pointer was correctly set in the aux helper struct.

Two main operations are provided on the registers read and write. The
address of the register to be read or written is given using lseek. The
seek position is updated upon read or write.

v2:
 - lseek is used to select the register to read/write
 - read/write are used instead of ioctl
 - no blocking_notifier is used, just a direct callback

v3:
 - use drm_dp_aux_dev prefix for public functions
 - chardev is named drm_dp_auxN
 - read/write don't allocate a buffer anymore, and transfer up to 16 bytes a
   time
 - remove notifier list from the implementation
 - option on menuconfig is now a boolean
 - add inline stub functions to avoid breakage when this option is disabled

v4:
 - fix build system changes - actually disable this module when not selected.

v5:
 - Use kref to avoid device closing while still in use 
 - Don't use list, use an idr for storing aux_dev
 - Remove "connector" attribute
 - set aux.dev to the connector drm_connector device, instead of
   drm_device

v6:
 - Use atomic_t for usage count
 - Use a mutex instead of spinlock for idr lock
 - Destroy chardev immediately on unregister
 - other minor suggestions from Ville

v7:
 - style fixes
 - error handling fixes

Signed-off-by: Rafael Antognolli 
---
 drivers/gpu/drm/Kconfig  |   8 +
 drivers/gpu/drm/Makefile |   1 +
 drivers/gpu/drm/drm_dp_aux_dev.c | 374 +++
 drivers/gpu/drm/drm_dp_helper.c  |   5 +
 include/drm/drm_dp_aux_dev.h |  50 ++
 5 files changed, 438 insertions(+)
 create mode 100644 drivers/gpu/drm/drm_dp_aux_dev.c
 create mode 100644 include/drm/drm_dp_aux_dev.h

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index c4bf9a1..daefcce 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -25,6 +25,14 @@ config DRM_MIPI_DSI
bool
depends on DRM
 
+config DRM_DP_AUX_CHARDEV
+   bool "DRM DP AUX Interface"
+   depends on DRM
+   help
+ Choose this option to enable a /dev/drm_dp_auxN node that allows to
+ read and write values to arbitrary DPCD registers on the DP aux
+ channel.
+
 config DRM_KMS_HELPER
tristate
depends on DRM
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 1e9ff4c..e48ec8f 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -28,6 +28,7 @@ drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o 
drm_probe_helper.o \
 drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
 drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
 drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o
+drm_kms_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o
 
 obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
 
diff --git a/drivers/gpu/drm/drm_dp_aux_dev.c b/drivers/gpu/drm/drm_dp_aux_dev.c
new file mode 100644
index 000..1a3ca39
--- /dev/null
+++ b/drivers/gpu/drm/drm_dp_aux_dev.c
@@ -0,0 +1,374 @@
+/*
+ * Copyright © 2015 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Authors:
+ *Rafael Antognolli 
+ *
+ */
+
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+
+struct drm_dp_aux_dev {
+   unsigned index;
+   struct drm_dp_aux *aux;
+   struct device *dev;
+   struct kref refcount;
+   atomic_t usecount;
+};
+
+#define DRM_AUX_MINORS 256
+#define AUX_MAX_OFFSET (1 << 20)
+static DEFINE_IDR(aux_idr);
+static 

Re: [Intel-gfx] [PATCH v7 1/2] drm/dp: Add a drm_aux-dev module for reading/writing dpcd registers.

[Ville Syrjälä]

On Fri, Oct 30, 2015 at 03:36:28PM -0700, Rafael Antognolli wrote:
> This module is heavily based on i2c-dev. Once loaded, it provides one
> dev node per DP AUX channel, named drm_dp_auxN, where N is an integer.
> 
> It's possible to know which connector owns this aux channel by looking
> at the respective sysfs /sys/class/drm_aux_dev/drm_dp_auxN/connector, if
> the connector device pointer was correctly set in the aux helper struct.
> 
> Two main operations are provided on the registers read and write. The
> address of the register to be read or written is given using lseek. The
> seek position is updated upon read or write.
> 
> v2:
>  - lseek is used to select the register to read/write
>  - read/write are used instead of ioctl
>  - no blocking_notifier is used, just a direct callback
> 
> v3:
>  - use drm_dp_aux_dev prefix for public functions
>  - chardev is named drm_dp_auxN
>  - read/write don't allocate a buffer anymore, and transfer up to 16 bytes a
>time
>  - remove notifier list from the implementation
>  - option on menuconfig is now a boolean
>  - add inline stub functions to avoid breakage when this option is disabled
> 
> v4:
>  - fix build system changes - actually disable this module when not selected.
> 
> v5:
>  - Use kref to avoid device closing while still in use 
>  - Don't use list, use an idr for storing aux_dev
>  - Remove "connector" attribute
>  - set aux.dev to the connector drm_connector device, instead of
>drm_device
> 
> v6:
>  - Use atomic_t for usage count
>  - Use a mutex instead of spinlock for idr lock
>  - Destroy chardev immediately on unregister
>  - other minor suggestions from Ville
> 
> v7:
>  - style fixes
>  - error handling fixes
> 
> Signed-off-by: Rafael Antognolli 
> ---
>  drivers/gpu/drm/Kconfig  |   8 +
>  drivers/gpu/drm/Makefile |   1 +
>  drivers/gpu/drm/drm_dp_aux_dev.c | 374 
> +++
>  drivers/gpu/drm/drm_dp_helper.c  |   5 +
>  include/drm/drm_dp_aux_dev.h |  50 ++
>  5 files changed, 438 insertions(+)
>  create mode 100644 drivers/gpu/drm/drm_dp_aux_dev.c
>  create mode 100644 include/drm/drm_dp_aux_dev.h
> 
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index c4bf9a1..daefcce 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -25,6 +25,14 @@ config DRM_MIPI_DSI
>   bool
>   depends on DRM
>  
> +config DRM_DP_AUX_CHARDEV
> + bool "DRM DP AUX Interface"
> + depends on DRM
> + help
> +   Choose this option to enable a /dev/drm_dp_auxN node that allows to
> +   read and write values to arbitrary DPCD registers on the DP aux
> +   channel.
> +
>  config DRM_KMS_HELPER
>   tristate
>   depends on DRM
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 1e9ff4c..e48ec8f 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -28,6 +28,7 @@ drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o 
> drm_probe_helper.o \
>  drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
>  drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
>  drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o
> +drm_kms_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o
>  
>  obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
>  
> diff --git a/drivers/gpu/drm/drm_dp_aux_dev.c 
> b/drivers/gpu/drm/drm_dp_aux_dev.c
> new file mode 100644
> index 000..1a3ca39
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_dp_aux_dev.c
> @@ -0,0 +1,374 @@
> +/*
> + * Copyright © 2015 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
> DEALINGS
> + * IN THE SOFTWARE.
> + *
> + * Authors:
> + *Rafael Antognolli 
> + *
> + */
> +
> +#include 
> +#include 
> +#include 
> +#include 
> +#include 
> +#include 
> +#include 
>