Add support for selecting memory type (MMAP or DMABUF)

Enable configuring vcam device memory type via user-space tool and driver.
Users can now specify whether to use MMAP or DMABUF for buffer management.

Author: liangchingyun

README.md

@@ -27,7 +27,7 @@ After running `make`, you should be able to generate the following files:
 
 Before loading this kernel module, you have to satisfy its dependency:
 ```shell
-$ sudo modprobe -a videobuf2_vmalloc videobuf2_v4l2
+$ sudo modprobe -a videobuf2_vmalloc videobuf2_v4l2 videobuf2-dma-contig
 ```
 
 The module can be loaded to Linux kernel by runnning the command:
@@ -56,7 +56,7 @@ $ sudo ./vcam-util -l
 You should get:
 ```
 Available virtual V4L2 compatible devices:
-1. fbX(640,480,rgb24) -> /dev/video0
+1. fbX(640,480,rgb24,mmap) -> /dev/video0
 ```
 
 You can use this command to check if the driver is ok:

control.c

@@ -73,6 +73,7 @@ static int control_iocontrol_get_device(struct vcam_device_spec *dev_spec)
     dev_spec->width = dev->fb_spec.xres_virtual;
     dev_spec->height = dev->fb_spec.yres_virtual;
     dev_spec->pix_fmt = dev->fb_spec.pix_fmt;
+    dev_spec->mem_type = dev->fb_spec.mem_type;
     dev_spec->cropratio = dev->fb_spec.cropratio;
 
     strncpy((char *) &dev_spec->fb_node, (const char *) vcamfb_get_devnode(dev),
@@ -174,6 +175,7 @@ static struct vcam_device_spec default_vcam_spec = {
     .height = 480,
     .cropratio = {.numerator = 3, .denominator = 4},
     .pix_fmt = VCAM_PIXFMT_RGB24,
+    .mem_type = VCAM_MEMORY_MMAP,
 };
 
 int request_vcam_device(struct vcam_device_spec *dev_spec)

device.h

@@ -89,6 +89,9 @@ struct vcam_device {
     struct v4l2_pix_format output_format;
     struct v4l2_pix_format input_format;
 
+    /* Memory type */
+    memtype_t mem_type;
+
     /* Conversion switches */
     bool conv_pixfmt_on;
     bool conv_res_on;

vcam-util.c

@@ -10,14 +10,14 @@
 
 #include "vcam.h"
 
-static const char *short_options = "hcm:r:ls:p:d:";
+static const char *short_options = "hcm:r:ls:p:d:t:";
 
 const struct option long_options[] = {
-    {"help", 0, NULL, 'h'},   {"create", 0, NULL, 'c'},
-    {"modify", 1, NULL, 'm'}, {"list", 0, NULL, 'l'},
-    {"size", 1, NULL, 's'},   {"pixfmt", 1, NULL, 'p'},
-    {"device", 1, NULL, 'd'}, {"remove", 1, NULL, 'r'},
-    {NULL, 0, NULL, 0}};
+    {"help", 0, NULL, 'h'},    {"create", 0, NULL, 'c'},
+    {"modify", 1, NULL, 'm'},  {"list", 0, NULL, 'l'},
+    {"size", 1, NULL, 's'},    {"pixfmt", 1, NULL, 'p'},
+    {"device", 1, NULL, 'd'},  {"remove", 1, NULL, 'r'},
+    {"memtype", 1, NULL, 't'}, {NULL, 0, NULL, 0}};
 
 const char *help =
     " -h --help                            Print this informations.\n"
@@ -37,6 +37,7 @@ const char *help =
     "and apply with crop ratio.\n"
     "\n"
     " -p --pixfmt  pix_fmt                 Specify pixel format (rgb24,yuyv).\n"
+    " -t --memtype mem_type                Specify memory type (mmap,dmabuf).\n"
     " -d --device  /dev/*                  Control device node.\n";
 
 enum ACTION { ACTION_NONE, ACTION_CREATE, ACTION_DESTROY, ACTION_MODIFY };
@@ -45,6 +46,7 @@ struct vcam_device_spec device_template = {
     .width = 640,
     .height = 480,
     .pix_fmt = VCAM_PIXFMT_RGB24,
+    .mem_type = VCAM_MEMORY_MMAP,
     .video_node = "",
     .fb_node = "",
 };
@@ -102,6 +104,14 @@ int determine_pixfmt(char *pixfmt_str)
     return -1;
 }
 
+int determine_memtype(char *memtype_str)
+{
+    if (!strncmp(memtype_str, "mmap", 4))
+        return VCAM_MEMORY_MMAP;
+    if (!strncmp(memtype_str, "dmabuf", 6))
+        return VCAM_MEMORY_DMABUF;
+    return -1;
+}
 int create_device(struct vcam_device_spec *dev)
 {
     int fd = open(ctl_path, O_RDWR);
@@ -118,6 +128,9 @@ int create_device(struct vcam_device_spec *dev)
     if (!dev->pix_fmt)
         dev->pix_fmt = device_template.pix_fmt;
 
+    if (!dev->mem_type)
+        dev->mem_type = device_template.mem_type;
+
     int res = ioctl(fd, VCAM_IOCTL_CREATE_DEVICE, dev);
     if (res) {
         fprintf(stderr, "Failed to create a new device.\n");
@@ -170,6 +183,9 @@ int modify_device(struct vcam_device_spec *dev)
     if (!dev->pix_fmt)
         dev->pix_fmt = orig_dev.pix_fmt;
 
+    if (!dev->mem_type)
+        dev->mem_type = orig_dev.mem_type;
+
     if (!dev->cropratio.numerator || !dev->cropratio.denominator)
         dev->cropratio = orig_dev.cropratio;
 
@@ -195,10 +211,11 @@ int list_devices()
     printf("Available virtual V4L2 compatible devices:\n");
     while (!ioctl(fd, VCAM_IOCTL_GET_DEVICE, &dev)) {
         dev.idx++;
-        printf("%d. %s(%d,%d,%d/%d,%s) -> %s\n", dev.idx, dev.fb_node,
+        printf("%d. %s(%d,%d,%d/%d,%s,%s) -> %s\n", dev.idx, dev.fb_node,
                dev.width, dev.height, dev.cropratio.numerator,
                dev.cropratio.denominator,
                dev.pix_fmt == VCAM_PIXFMT_RGB24 ? "rgb24" : "yuyv",
+               dev.mem_type == VCAM_MEMORY_MMAP ? "mmap" : "dmabuf",
                dev.video_node);
     }
     close(fd);
@@ -258,6 +275,16 @@ int main(int argc, char *argv[])
             dev.pix_fmt = (char) tmp;
             printf("Setting pixel format to %s.\n", optarg);
             break;
+        case 't':
+            tmp = determine_memtype(optarg);
+            if (tmp < 0) {
+                fprintf(stderr, "Failed to recognize memory type %s.\n",
+                        optarg);
+                exit(-1);
+            }
+            dev.mem_type = (char) tmp;
+            printf("Setting memory type to %s.\n", optarg);
+            break;
         case 'd':
             printf("Using device %s.\n", optarg);
             strncpy(ctl_path, optarg, sizeof(ctl_path) - 1);

vcam.h

@@ -10,6 +10,7 @@
 #define VCAM_IOCTL_MODIFY_SETTING 0x555
 
 typedef enum { VCAM_PIXFMT_RGB24 = 0x01, VCAM_PIXFMT_YUYV = 0x02 } pixfmt_t;
+typedef enum { VCAM_MEMORY_MMAP = 0, VCAM_MEMORY_DMABUF = 2 } memtype_t;
 
 struct crop_ratio {
     __u32 numerator;
@@ -27,6 +28,7 @@ struct vcam_device_spec {
     struct crop_ratio cropratio;
 
     pixfmt_t pix_fmt;
+    memtype_t mem_type;
     char video_node[64];
     char fb_node[64];
 };

videobuf.c

@@ -4,6 +4,7 @@
 #include <linux/vmalloc.h>
 #include <media/videobuf2-core.h>
 #include <media/videobuf2-dma-contig.h>
+#include <media/videobuf2-vmalloc.h>
 
 #include "videobuf.h"
 
@@ -153,7 +154,15 @@ int vcam_out_videobuf2_setup(struct vcam_device *dev)
     q->buf_struct_size = sizeof(struct vcam_out_buffer);
     q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
     q->ops = &vcam_vb2_ops;
-    q->mem_ops = &vb2_dma_contig_memops;
+    pr_info("memory type %d\n", dev->mem_type);
+    switch (dev->mem_type) {
+    case VCAM_MEMORY_MMAP:
+        q->mem_ops = &vb2_vmalloc_memops;
+        break;
+    case VCAM_MEMORY_DMABUF:
+        q->mem_ops = &vb2_dma_contig_memops;
+        break;
+    }
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 8, 0)
     q->min_queued_buffers = 2;
 #else