Replace BUG_ON() calls with proper checks to prevent unnecessary kernel
panics. Return appropriate error codes (-EINVAL or -EFAULT) instead of
crashing the system.

Signed-off-by: Olle Lukowski <olle@lukowski.dev>
---
 drivers/staging/most/dim2/dim2.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/staging/most/dim2/dim2.c b/drivers/staging/most/dim2/dim2.c
index dad2abe6c..d0832704b 100644
--- a/drivers/staging/most/dim2/dim2.c
+++ b/drivers/staging/most/dim2/dim2.c
@@ -166,8 +166,10 @@ static int try_start_dim_transfer(struct hdm_channel *hdm_ch)
 	unsigned long flags;
 	struct dim_ch_state st;
 
-	BUG_ON(!hdm_ch);
-	BUG_ON(!hdm_ch->is_initialized);
+	if (!hdm_ch)
+		return -EINVAL;
+	if (!hdm_ch->is_initialized)
+		return -EINVAL;
 
 	spin_lock_irqsave(&dim_lock, flags);
 	if (list_empty(head)) {
@@ -188,7 +190,11 @@ static int try_start_dim_transfer(struct hdm_channel *hdm_ch)
 		return -EAGAIN;
 	}
 
-	BUG_ON(mbo->bus_address == 0);
+	if (mbo->bus_address == 0) {
+		spin_unlock_irqrestore(&dim_lock, flags);
+		return -EFAULT;
+	}
+
 	if (!dim_enqueue_buffer(&hdm_ch->ch, mbo->bus_address, buf_size)) {
 		list_del(head->next);
 		spin_unlock_irqrestore(&dim_lock, flags);
@@ -269,8 +275,10 @@ static void service_done_flag(struct dim2_hdm *dev, int ch_idx)
 	unsigned long flags;
 	u8 *data;
 
-	BUG_ON(!hdm_ch);
-	BUG_ON(!hdm_ch->is_initialized);
+	if (!hdm_ch)
+		return;
+	if (!hdm_ch->is_initialized)
+		return;
 
 	spin_lock_irqsave(&dim_lock, flags);
 
@@ -455,7 +463,8 @@ static int configure_channel(struct most_interface *most_iface, int ch_idx,
 	int const ch_addr = ch_idx * 2 + 2;
 	struct hdm_channel *const hdm_ch = dev->hch + ch_idx;
 
-	BUG_ON(ch_idx < 0 || ch_idx >= DMA_CHANNELS);
+	if (ch_idx < 0 || ch_idx >= DMA_CHANNELS)
+		return -EINVAL;
 
 	if (hdm_ch->is_initialized)
 		return -EPERM;
@@ -567,7 +576,8 @@ static int enqueue(struct most_interface *most_iface, int ch_idx,
 	struct hdm_channel *hdm_ch = dev->hch + ch_idx;
 	unsigned long flags;
 
-	BUG_ON(ch_idx < 0 || ch_idx >= DMA_CHANNELS);
+	if (ch_idx < 0 || ch_idx >= DMA_CHANNELS)
+		return -EINVAL;
 
 	if (!hdm_ch->is_initialized)
 		return -EPERM;
@@ -643,7 +653,8 @@ static int poison_channel(struct most_interface *most_iface, int ch_idx)
 	u8 hal_ret;
 	int ret = 0;
 
-	BUG_ON(ch_idx < 0 || ch_idx >= DMA_CHANNELS);
+	if (ch_idx < 0 || ch_idx >= DMA_CHANNELS)
+		return -EINVAL;
 
 	if (!hdm_ch->is_initialized)
 		return -EPERM;

-- 
2.51.1

On Tue, Oct 21, 2025 at 04:09:29PM +0300, Olle Lukowski wrote:
> Replace BUG_ON() calls with proper checks to prevent unnecessary kernel
> panics. Return appropriate error codes (-EINVAL or -EFAULT) instead of
> crashing the system.
> 
> Signed-off-by: Olle Lukowski <olle@lukowski.dev>
> ---
>  drivers/staging/most/dim2/dim2.c | 27 +++++++++++++++++++--------
>  1 file changed, 19 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/staging/most/dim2/dim2.c b/drivers/staging/most/dim2/dim2.c
> index dad2abe6c..d0832704b 100644
> --- a/drivers/staging/most/dim2/dim2.c
> +++ b/drivers/staging/most/dim2/dim2.c
> @@ -166,8 +166,10 @@ static int try_start_dim_transfer(struct hdm_channel *hdm_ch)
>  	unsigned long flags;
>  	struct dim_ch_state st;
>  
> -	BUG_ON(!hdm_ch);
> -	BUG_ON(!hdm_ch->is_initialized);
> +	if (!hdm_ch)
> +		return -EINVAL;
> +	if (!hdm_ch->is_initialized)
> +		return -EINVAL;

Can these things ever actually happen?  In looking at the code, I don't
see how that could be, do you?

Let's not check for things that are impossible to ever hit.

Same with the other changes in this series, please verify that these are
actually possible to happen.  If not, then just remove the check.

>  	spin_lock_irqsave(&dim_lock, flags);
>  	if (list_empty(head)) {
> @@ -188,7 +190,11 @@ static int try_start_dim_transfer(struct hdm_channel *hdm_ch)
>  		return -EAGAIN;
>  	}
>  
> -	BUG_ON(mbo->bus_address == 0);
> +	if (mbo->bus_address == 0) {
> +		spin_unlock_irqrestore(&dim_lock, flags);
> +		return -EFAULT;

You need to do more than just that here :(

Please be very careful on error paths to properly clean up everything.

thanks,

greg k-h