Hi Martin,
On 12/09/2023 14:07, tumic@xxxxxxxxxx wrote:
> From: Martin Tůma <martin.tuma@xxxxxxxxxxxxxxxxxxxxx>
>
> Digiteq Automotive MGB4 is a modular frame grabber PCIe card for automotive
> video interfaces. As for now, two modules - FPD-Link and GMSL - are
> available and supported by the driver. The card has two inputs and two
> outputs (FPD-Link only).
>
> In addition to the video interfaces it also provides a trigger signal
> interface and a MTD interface for FPGA firmware upload.
>
> Signed-off-by: Martin Tůma <martin.tuma@xxxxxxxxxxxxxxxxxxxxx>
> ---
<snip>
> +static ssize_t video_source_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct video_device *vdev = to_video_device(dev);
> + struct mgb4_vout_dev *voutdev = video_get_drvdata(vdev);
> + u32 config = mgb4_read_reg(&voutdev->mgbdev->video,
> + voutdev->config->regs.config);
> +
> + return sprintf(buf, "%u\n", (config & 0xc) >> 2);
> +}
> +
> +static ssize_t video_source_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct video_device *vdev = to_video_device(dev);
> + struct mgb4_vout_dev *voutdev = video_get_drvdata(vdev);
> + struct mgb4_dev *mgbdev = voutdev->mgbdev;
> + struct mgb4_vin_dev *loopin_new = 0, *loopin_old = 0;
> + unsigned long val;
> + unsigned long flags_in[MGB4_VIN_DEVICES], flags_out[MGB4_VOUT_DEVICES];
> + ssize_t ret;
> + u32 config;
> + int i;
> +
> + memset(flags_in, 0, sizeof(flags_in));
> + memset(flags_out, 0, sizeof(flags_out));
> +
> + ret = kstrtoul(buf, 10, &val);
> + if (ret)
> + return ret;
> + if (val > 3)
> + return -EINVAL;
> +
> + for (i = 0; i < MGB4_VIN_DEVICES; i++)
> + if (mgbdev->vin[i])
> + spin_lock_irqsave(&mgbdev->vin[i]->vdev.fh_lock,
> + flags_in[i]);
> + for (i = 0; i < MGB4_VOUT_DEVICES; i++)
> + if (mgbdev->vout[i])
> + spin_lock_irqsave(&mgbdev->vout[i]->vdev.fh_lock,
> + flags_out[i]);
I missed this in my review: never use fh_lock, that's for internal use only.
Instead, use the vdev->lock mutex.
> +
> + ret = -EBUSY;
> + for (i = 0; i < MGB4_VIN_DEVICES; i++)
> + if (mgbdev->vin[i] && !list_empty(&mgbdev->vin[i]->vdev.fh_list))
> + goto error;
This is also wrong, the key moment at which such changes are no longer allowed
is when you allocate buffers for the first time. Use vb2_is_busy() to detect that.
>From what I can see in the code most store functions operate on a single video device,
so for those using mutex_lock_interruptible(vdev->lock) and vb2_is_busy() will do the
trick.
For this store function that needs to check all devices it is more complicated.
I think the best approach would be to create a top-level field 'reconfig_in_progress'
(or something along those lines), protected by a spinlock.
At the start this function will take the lock, check if reconfig is already in progress
and just return EBUSY here. Otherwise it sets reconfig_in_progress to true and unlocks
the lock.
After that for each video device you take the vdev->lock, check if vb2_is_busy() and
unlock vdev->lock. If any is busy, then set reconfig_in_progress back to false and
return EBUSY here.
To prevent another process from creating buffers, you have to check in the queue_setup
functions if a reconfig is in progress and return EBUSY there.
This scheme avoids having to lock ALL video devices (bad practice), and it should
also avoid this smatch warning.
Note: instead of using a spinlock I think you can also use test_and_set_bit: that's
atomic and you can avoid adding a spinlock.
Regards,
Hans
> + for (i = 0; i < MGB4_VOUT_DEVICES; i++)
> + if (mgbdev->vout[i] && !list_empty(&mgbdev->vout[i]->vdev.fh_list))
> + goto error;
> +
> + config = mgb4_read_reg(&mgbdev->video, voutdev->config->regs.config);
> +
> + if (((config & 0xc) >> 2) < MGB4_VIN_DEVICES)
> + loopin_old = mgbdev->vin[(config & 0xc) >> 2];
> + if (val < MGB4_VIN_DEVICES)
> + loopin_new = mgbdev->vin[val];
> + if (loopin_old && loopin_cnt(loopin_old) == 1)
> + mgb4_mask_reg(&mgbdev->video, loopin_old->config->regs.config,
> + 0x2, 0x0);
> + if (loopin_new)
> + mgb4_mask_reg(&mgbdev->video, loopin_new->config->regs.config,
> + 0x2, 0x2);
> +
> + if (val == voutdev->config->id + MGB4_VIN_DEVICES)
> + mgb4_write_reg(&mgbdev->video, voutdev->config->regs.config,
> + config & ~(1 << 1));
> + else
> + mgb4_write_reg(&mgbdev->video, voutdev->config->regs.config,
> + config | (1U << 1));
> +
> + mgb4_mask_reg(&mgbdev->video, voutdev->config->regs.config, 0xc,
> + val << 2);
> +
> + ret = count;
> +
> +error:
> + for (i = MGB4_VOUT_DEVICES - 1; i >= 0; i--)
> + if (mgbdev->vout[i])
> + spin_unlock_irqrestore(&mgbdev->vout[i]->vdev.fh_lock,
> + flags_out[i]);
> + for (i = MGB4_VIN_DEVICES - 1; i >= 0; i--)
> + if (mgbdev->vin[i])
> + spin_unlock_irqrestore(&mgbdev->vin[i]->vdev.fh_lock,
> + flags_in[i]);
> +
> + return ret;
> +}
