media: dvb-ttusb-budget: don't use stack for USB transfers

As reported by smatch:

    drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c:311 ttusb_boot_dsp() error: doing dma on the stack (b)
    drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c:321 ttusb_boot_dsp() error: doing dma on the stack (b)
    drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c:330 ttusb_boot_dsp() error: doing dma on the stack (b)
    drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c:351 ttusb_set_channel() error: doing dma on the stack (b)
    drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c:361 ttusb_del_channel() error: doing dma on the stack (b)
    drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c:412 ttusb_init_controller() error: doing dma on the stack (b0)
    drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c:416 ttusb_init_controller() error: doing dma on the stack (b1)
    drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c:422 ttusb_init_controller() error: doing dma on the stack (b2)
    drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c:425 ttusb_init_controller() error: doing dma on the stack (b3)
    drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c:430 ttusb_init_controller() error: doing dma on the stack (get_version)

This driver still uses the USB stack for DMA transfers,
which is broken for a long time. I almost dropped this driver,
as there's a high chance that nobody is using it with upstream
Kernels, as we didn't receive any bug reports.

As fixing this won't be hard, I ended opting to fix.

While here, I dropped an ugly hack that implemented read via
a separate function that was just doing a memcpy().

It should be noticed that, during the init phase, there's
a "b4" register that were never initialized, as its buffer
were used just to store the results of "b3" initialization.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

diff --git a/drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c b/drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c
index 4e56ff8..2582a62 100644 (file)
--- a/drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c
+++ b/drivers/media/usb/ttusb-budget/dvb-ttusb-budget.c
@@ -72,6 +72,9 @@ DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nr);
 #define TTUSB_REV_2_2  0x22
 #define TTUSB_BUDGET_NAME "ttusb_stc_fw"
 
+#define MAX_SEND       0x28
+#define MAX_RCV                0x20
+
 /*
  *  since we're casting (struct ttusb*) <-> (struct dvb_demux*) around
  *  the dvb_demux field must be the first in struct!!
@@ -119,87 +122,72 @@ struct ttusb {
        int cc;                 /* MuxCounter - will increment on EVERY MUX PACKET */
        /* (including stuffing. yes. really.) */
 
-       u8 last_result[32];
+       u8 send_buf[MAX_SEND];
+       u8 last_result[MAX_RCV];
 
        int revision;
 
        struct dvb_frontend* fe;
 };
 
-/* ugly workaround ... don't know why it's necessary to read */
-/* all result codes. */
-
-static int ttusb_cmd(struct ttusb *ttusb,
-             const u8 * data, int len, int needresult)
+static int ttusb_cmd(struct ttusb *ttusb, u8 *data, int len, int len_result)
 {
        int actual_len;
        int err;
-       int i;
-
-       if (debug >= 3) {
-               printk(KERN_DEBUG ">");
-               for (i = 0; i < len; ++i)
-                       printk(KERN_CONT " %02x", data[i]);
-               printk(KERN_CONT "\n");
-       }
 
        if (mutex_lock_interruptible(&ttusb->semusb) < 0)
                return -EAGAIN;
 
+       if (debug >= 3)
+               printk(KERN_DEBUG "> %*ph\n", len, data);
+
+       memcpy(data, ttusb->send_buf, len);
+
        err = usb_bulk_msg(ttusb->dev, ttusb->bulk_out_pipe,
-                          (u8 *) data, len, &actual_len, 1000);
+                          ttusb->send_buf, len, &actual_len, 1000);
        if (err != 0) {
                dprintk("%s: usb_bulk_msg(send) failed, err == %i!\n",
                        __func__, err);
-               mutex_unlock(&ttusb->semusb);
-               return err;
+               goto err;
        }
        if (actual_len != len) {
+               err = -EIO;
                dprintk("%s: only wrote %d of %d bytes\n", __func__,
                        actual_len, len);
-               mutex_unlock(&ttusb->semusb);
-               return -1;
+               goto err;
        }
 
        err = usb_bulk_msg(ttusb->dev, ttusb->bulk_in_pipe,
-                          ttusb->last_result, 32, &actual_len, 1000);
+                          ttusb->last_result, MAX_RCV, &actual_len, 1000);
 
        if (err != 0) {
                printk("%s: failed, receive error %d\n", __func__,
                       err);
-               mutex_unlock(&ttusb->semusb);
-               return err;
+               goto err;
        }
 
        if (debug >= 3) {
                actual_len = ttusb->last_result[3] + 4;
-               printk(KERN_DEBUG "<");
-               for (i = 0; i < actual_len; ++i)
-                       printk(KERN_CONT " %02x", ttusb->last_result[i]);
-               printk(KERN_CONT "\n");
+               printk(KERN_DEBUG "< %*ph\n", actual_len, ttusb->last_result);
        }
 
-       if (!needresult)
-               mutex_unlock(&ttusb->semusb);
-       return 0;
-}
+       if (len_result)
+               memcpy(ttusb->send_buf, ttusb->last_result, len_result);
 
-static int ttusb_result(struct ttusb *ttusb, u8 * data, int len)
-{
-       memcpy(data, ttusb->last_result, len);
+err:
        mutex_unlock(&ttusb->semusb);
-       return 0;
+       return err;
 }
 
 static int ttusb_i2c_msg(struct ttusb *ttusb,
                  u8 addr, u8 * snd_buf, u8 snd_len, u8 * rcv_buf,
                  u8 rcv_len)
 {
-       u8 b[0x28];
+       u8 b[MAX_SEND];
        u8 id = ++ttusb->c;
        int i, err;
 
-       if (snd_len > 0x28 - 7 || rcv_len > 0x20 - 7)
+       if (snd_len > MAX_SEND - 7 || rcv_len > MAX_RCV - 7)
                return -EINVAL;
 
        b[0] = 0xaa;
@@ -213,13 +201,11 @@ static int ttusb_i2c_msg(struct ttusb *ttusb,
        for (i = 0; i < snd_len; i++)
                b[7 + i] = snd_buf[i];
 
-       err = ttusb_cmd(ttusb, b, snd_len + 7, 1);
+       err = ttusb_cmd(ttusb, b, snd_len + 7, MAX_RCV);
 
        if (err)
                return -EREMOTEIO;
 
-       err = ttusb_result(ttusb, b, 0x20);
-
        /* check if the i2c transaction was successful */
        if ((snd_len != b[5]) || (rcv_len != b[6])) return -EREMOTEIO;
 
@@ -400,8 +386,6 @@ static int ttusb_init_controller(struct ttusb *ttusb)
        /* i2c write read: 5 bytes, addr 0x10, 0x02 bytes write, 1 bytes read. */
        u8 b3[] =
            { 0xaa, ++ttusb->c, 0x31, 5, 0x10, 0x02, 0x01, 0x00, 0x1e };
-       u8 b4[] =
-           { 0x55, ttusb->c, 0x31, 4, 0x10, 0x02, 0x01, 0x00, 0x1e };
 
        u8 get_version[] = { 0xaa, ++ttusb->c, 0x17, 5, 0, 0, 0, 0, 0 };
        u8 get_dsp_version[0x20] =
@@ -422,15 +406,11 @@ static int ttusb_init_controller(struct ttusb *ttusb)
        if ((err = ttusb_cmd(ttusb, b2, sizeof(b2), 0)))
                return err;
 
-       if ((err = ttusb_cmd(ttusb, b3, sizeof(b3), 1)))
+       if ((err = ttusb_cmd(ttusb, b3, sizeof(b3), 0)))
                return err;
 
-       err = ttusb_result(ttusb, b4, sizeof(b4));
-
-       if ((err = ttusb_cmd(ttusb, get_version, sizeof(get_version), 1)))
-               return err;
-
-       if ((err = ttusb_result(ttusb, get_version, sizeof(get_version))))
+       if ((err = ttusb_cmd(ttusb, get_version,
+                            sizeof(get_version), sizeof(get_version))))
                return err;
 
        dprintk("%s: stc-version: %c%c%c%c%c\n", __func__,
@@ -451,14 +431,11 @@ static int ttusb_init_controller(struct ttusb *ttusb)
                           (get_version[8] - '0');
 
        err =
-           ttusb_cmd(ttusb, get_dsp_version, sizeof(get_dsp_version), 1);
+           ttusb_cmd(ttusb, get_dsp_version,
+                     sizeof(get_dsp_version), sizeof(get_dsp_version));
        if (err)
                return err;
 
-       err =
-           ttusb_result(ttusb, get_dsp_version, sizeof(get_dsp_version));
-       if (err)
-               return err;
        printk("%s: dsp-version: %c%c%c\n", __func__,
               get_dsp_version[4], get_dsp_version[5], get_dsp_version[6]);
        return 0;