FAILED: patch "[PATCH] can: gs_usb: increase max interface to U8_MAX" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] can: gs_usb: increase max interface to U8_MAX" failed to apply to 5.15-stable tree

[gregkh]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 2a27f6a8fb5722223d526843040f747e9b0e8060
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025102039-detoxify-trustee-aa22@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2a27f6a8fb5722223d526843040f747e9b0e8060 Mon Sep 17 00:00:00 2001
From: Celeste Liu <uwu@coelacanthus.name>
Date: Tue, 30 Sep 2025 19:34:28 +0800
Subject: [PATCH] can: gs_usb: increase max interface to U8_MAX

This issue was found by Runcheng Lu when develop HSCanT USB to CAN FD
converter[1]. The original developers may have only 3 interfaces
device to test so they write 3 here and wait for future change.

During the HSCanT development, we actually used 4 interfaces, so the
limitation of 3 is not enough now. But just increase one is not
future-proofed. Since the channel index type in gs_host_frame is u8,
just make canch[] become a flexible array with a u8 index, so it
naturally constraint by U8_MAX and avoid statically allocate 256
pointer for every gs_usb device.

[1]: https://github.com/cherry-embedded/HSCanT-hardware

Fixes: d08e973a77d1 ("can: gs_usb: Added support for the GS_USB CAN devices")
Reported-by: Runcheng Lu <runcheng.lu@hpmicro.com>
Cc: stable@vger.kernel.org
Reviewed-by: Vincent Mailhol <mailhol@kernel.org>
Signed-off-by: Celeste Liu <uwu@coelacanthus.name>
Link: https://patch.msgid.link/20250930-gs-usb-max-if-v5-1-863330bf6666@coelacanthus.name
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/usb/gs_usb.c b/drivers/net/can/usb/gs_usb.c
index c9482d6e947b..9fb4cbbd6d6d 100644
--- a/drivers/net/can/usb/gs_usb.c
+++ b/drivers/net/can/usb/gs_usb.c
@@ -289,11 +289,6 @@ struct gs_host_frame {
 #define GS_MAX_RX_URBS 30
 #define GS_NAPI_WEIGHT 32
 
-/* Maximum number of interfaces the driver supports per device.
- * Current hardware only supports 3 interfaces. The future may vary.
- */
-#define GS_MAX_INTF 3
-
 struct gs_tx_context {
 	struct gs_can *dev;
 	unsigned int echo_id;
@@ -324,7 +319,6 @@ struct gs_can {
 
 /* usb interface struct */
 struct gs_usb {
-	struct gs_can *canch[GS_MAX_INTF];
 	struct usb_anchor rx_submitted;
 	struct usb_device *udev;
 
@@ -336,9 +330,11 @@ struct gs_usb {
 
 	unsigned int hf_size_rx;
 	u8 active_channels;
+	u8 channel_cnt;
 
 	unsigned int pipe_in;
 	unsigned int pipe_out;
+	struct gs_can *canch[] __counted_by(channel_cnt);
 };
 
 /* 'allocate' a tx context.
@@ -599,7 +595,7 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
 	}
 
 	/* device reports out of range channel id */
-	if (hf->channel >= GS_MAX_INTF)
+	if (hf->channel >= parent->channel_cnt)
 		goto device_detach;
 
 	dev = parent->canch[hf->channel];
@@ -699,7 +695,7 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
 	/* USB failure take down all interfaces */
 	if (rc == -ENODEV) {
 device_detach:
-		for (rc = 0; rc < GS_MAX_INTF; rc++) {
+		for (rc = 0; rc < parent->channel_cnt; rc++) {
 			if (parent->canch[rc])
 				netif_device_detach(parent->canch[rc]->netdev);
 		}
@@ -1460,17 +1456,19 @@ static int gs_usb_probe(struct usb_interface *intf,
 	icount = dconf.icount + 1;
 	dev_info(&intf->dev, "Configuring for %u interfaces\n", icount);
 
-	if (icount > GS_MAX_INTF) {
+	if (icount > type_max(parent->channel_cnt)) {
 		dev_err(&intf->dev,
 			"Driver cannot handle more that %u CAN interfaces\n",
-			GS_MAX_INTF);
+			type_max(parent->channel_cnt));
 		return -EINVAL;
 	}
 
-	parent = kzalloc(sizeof(*parent), GFP_KERNEL);
+	parent = kzalloc(struct_size(parent, canch, icount), GFP_KERNEL);
 	if (!parent)
 		return -ENOMEM;
 
+	parent->channel_cnt = icount;
+
 	init_usb_anchor(&parent->rx_submitted);
 
 	usb_set_intfdata(intf, parent);
@@ -1531,7 +1529,7 @@ static void gs_usb_disconnect(struct usb_interface *intf)
 		return;
 	}
 
-	for (i = 0; i < GS_MAX_INTF; i++)
+	for (i = 0; i < parent->channel_cnt; i++)
 		if (parent->canch[i])
 			gs_destroy_candev(parent->canch[i]);
 

[PATCH 5.15.y] can: gs_usb: increase max interface to U8_MAX

[Celeste Liu]

commit 2a27f6a8fb5722223d526843040f747e9b0e8060 upstream

This issue was found by Runcheng Lu when develop HSCanT USB to CAN FD
converter[1]. The original developers may have only 3 interfaces
device to test so they write 3 here and wait for future change.

During the HSCanT development, we actually used 4 interfaces, so the
limitation of 3 is not enough now. But just increase one is not
future-proofed. Since the channel index type in gs_host_frame is u8,
just make canch[] become a flexible array with a u8 index, so it
naturally constraint by U8_MAX and avoid statically allocate 256
pointer for every gs_usb device.

[1]: https://github.com/cherry-embedded/HSCanT-hardware

Fixes: d08e973a77d1 ("can: gs_usb: Added support for the GS_USB CAN devices")
Reported-by: Runcheng Lu <runcheng.lu@hpmicro.com>
Cc: stable@vger.kernel.org
Reviewed-by: Vincent Mailhol <mailhol@kernel.org>
Signed-off-by: Celeste Liu <uwu@coelacanthus.name>
Link: https://patch.msgid.link/20250930-gs-usb-max-if-v5-1-863330bf6666@coelacanthus.name
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/usb/gs_usb.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/drivers/net/can/usb/gs_usb.c b/drivers/net/can/usb/gs_usb.c
index 7dc4fb574e45..33800bb75064 100644
--- a/drivers/net/can/usb/gs_usb.c
+++ b/drivers/net/can/usb/gs_usb.c
@@ -157,10 +157,6 @@ struct gs_host_frame {
 #define GS_MAX_TX_URBS 10
 /* Only launch a max of GS_MAX_RX_URBS usb requests at a time. */
 #define GS_MAX_RX_URBS 30
-/* Maximum number of interfaces the driver supports per device.
- * Current hardware only supports 2 interfaces. The future may vary.
- */
-#define GS_MAX_INTF 2
 
 struct gs_tx_context {
 	struct gs_can *dev;
@@ -191,10 +187,11 @@ struct gs_can {
 
 /* usb interface struct */
 struct gs_usb {
-	struct gs_can *canch[GS_MAX_INTF];
 	struct usb_anchor rx_submitted;
 	struct usb_device *udev;
 	u8 active_channels;
+	u8 channel_cnt;
+	struct gs_can *canch[] __counted_by(channel_cnt);
 };
 
 /* 'allocate' a tx context.
@@ -322,7 +319,7 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
 	}
 
 	/* device reports out of range channel id */
-	if (hf->channel >= GS_MAX_INTF)
+	if (hf->channel >= usbcan->channel_cnt)
 		goto device_detach;
 
 	dev = usbcan->canch[hf->channel];
@@ -410,7 +407,7 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
 	/* USB failure take down all interfaces */
 	if (rc == -ENODEV) {
  device_detach:
-		for (rc = 0; rc < GS_MAX_INTF; rc++) {
+		for (rc = 0; rc < usbcan->channel_cnt; rc++) {
 			if (usbcan->canch[rc])
 				netif_device_detach(usbcan->canch[rc]->netdev);
 		}
@@ -993,20 +990,22 @@ static int gs_usb_probe(struct usb_interface *intf,
 	icount = dconf->icount + 1;
 	dev_info(&intf->dev, "Configuring for %d interfaces\n", icount);
 
-	if (icount > GS_MAX_INTF) {
+	if (icount > type_max(typeof(dev->channel_cnt))) {
 		dev_err(&intf->dev,
-			"Driver cannot handle more that %d CAN interfaces\n",
-			GS_MAX_INTF);
+			"Driver cannot handle more that %u CAN interfaces\n",
+			type_max(typeof(dev->channel_cnt)));
 		kfree(dconf);
 		return -EINVAL;
 	}
 
-	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	dev = kzalloc(struct_size(dev, canch, icount), GFP_KERNEL);
 	if (!dev) {
 		kfree(dconf);
 		return -ENOMEM;
 	}
 
+	dev->channel_cnt = icount;
+
 	init_usb_anchor(&dev->rx_submitted);
 
 	usb_set_intfdata(intf, dev);
@@ -1047,7 +1046,7 @@ static void gs_usb_disconnect(struct usb_interface *intf)
 		return;
 	}
 
-	for (i = 0; i < GS_MAX_INTF; i++)
+	for (i = 0; i < dev->channel_cnt; i++)
 		if (dev->canch[i])
 			gs_destroy_candev(dev->canch[i]);
 
-- 
2.51.1.dirty

Re: [PATCH 5.15.y] can: gs_usb: increase max interface to U8_MAX

[Greg KH]

On Mon, Oct 20, 2025 at 08:25:30PM +0800, Celeste Liu wrote:
> commit 2a27f6a8fb5722223d526843040f747e9b0e8060 upstream
> 
> This issue was found by Runcheng Lu when develop HSCanT USB to CAN FD
> converter[1]. The original developers may have only 3 interfaces
> device to test so they write 3 here and wait for future change.
> 
> During the HSCanT development, we actually used 4 interfaces, so the
> limitation of 3 is not enough now. But just increase one is not
> future-proofed. Since the channel index type in gs_host_frame is u8,
> just make canch[] become a flexible array with a u8 index, so it
> naturally constraint by U8_MAX and avoid statically allocate 256
> pointer for every gs_usb device.
> 
> [1]: https://github.com/cherry-embedded/HSCanT-hardware
> 
> Fixes: d08e973a77d1 ("can: gs_usb: Added support for the GS_USB CAN devices")
> Reported-by: Runcheng Lu <runcheng.lu@hpmicro.com>
> Cc: stable@vger.kernel.org
> Reviewed-by: Vincent Mailhol <mailhol@kernel.org>
> Signed-off-by: Celeste Liu <uwu@coelacanthus.name>
> Link: https://patch.msgid.link/20250930-gs-usb-max-if-v5-1-863330bf6666@coelacanthus.name
> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
> ---
>  drivers/net/can/usb/gs_usb.c | 23 +++++++++++------------
>  1 file changed, 11 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/can/usb/gs_usb.c b/drivers/net/can/usb/gs_usb.c
> index 7dc4fb574e45..33800bb75064 100644
> --- a/drivers/net/can/usb/gs_usb.c
> +++ b/drivers/net/can/usb/gs_usb.c
> @@ -157,10 +157,6 @@ struct gs_host_frame {
>  #define GS_MAX_TX_URBS 10
>  /* Only launch a max of GS_MAX_RX_URBS usb requests at a time. */
>  #define GS_MAX_RX_URBS 30
> -/* Maximum number of interfaces the driver supports per device.
> - * Current hardware only supports 2 interfaces. The future may vary.
> - */
> -#define GS_MAX_INTF 2
>  
>  struct gs_tx_context {
>  	struct gs_can *dev;
> @@ -191,10 +187,11 @@ struct gs_can {
>  
>  /* usb interface struct */
>  struct gs_usb {
> -	struct gs_can *canch[GS_MAX_INTF];
>  	struct usb_anchor rx_submitted;
>  	struct usb_device *udev;
>  	u8 active_channels;
> +	u8 channel_cnt;
> +	struct gs_can *canch[] __counted_by(channel_cnt);
>  };
>  
>  /* 'allocate' a tx context.
> @@ -322,7 +319,7 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
>  	}
>  
>  	/* device reports out of range channel id */
> -	if (hf->channel >= GS_MAX_INTF)
> +	if (hf->channel >= usbcan->channel_cnt)
>  		goto device_detach;
>  
>  	dev = usbcan->canch[hf->channel];
> @@ -410,7 +407,7 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
>  	/* USB failure take down all interfaces */
>  	if (rc == -ENODEV) {
>   device_detach:
> -		for (rc = 0; rc < GS_MAX_INTF; rc++) {
> +		for (rc = 0; rc < usbcan->channel_cnt; rc++) {
>  			if (usbcan->canch[rc])
>  				netif_device_detach(usbcan->canch[rc]->netdev);
>  		}
> @@ -993,20 +990,22 @@ static int gs_usb_probe(struct usb_interface *intf,
>  	icount = dconf->icount + 1;
>  	dev_info(&intf->dev, "Configuring for %d interfaces\n", icount);
>  
> -	if (icount > GS_MAX_INTF) {
> +	if (icount > type_max(typeof(dev->channel_cnt))) {
>  		dev_err(&intf->dev,
> -			"Driver cannot handle more that %d CAN interfaces\n",
> -			GS_MAX_INTF);
> +			"Driver cannot handle more that %u CAN interfaces\n",
> +			type_max(typeof(dev->channel_cnt)));
>  		kfree(dconf);
>  		return -EINVAL;
>  	}
>  
> -	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
> +	dev = kzalloc(struct_size(dev, canch, icount), GFP_KERNEL);
>  	if (!dev) {
>  		kfree(dconf);
>  		return -ENOMEM;
>  	}
>  
> +	dev->channel_cnt = icount;
> +
>  	init_usb_anchor(&dev->rx_submitted);
>  
>  	usb_set_intfdata(intf, dev);
> @@ -1047,7 +1046,7 @@ static void gs_usb_disconnect(struct usb_interface *intf)
>  		return;
>  	}
>  
> -	for (i = 0; i < GS_MAX_INTF; i++)
> +	for (i = 0; i < dev->channel_cnt; i++)
>  		if (dev->canch[i])
>  			gs_destroy_candev(dev->canch[i]);
>  
> -- 
> 2.51.1.dirty
> 
> 

Breaks the build :(

Re: [PATCH 5.15.y] can: gs_usb: increase max interface to U8_MAX

[Celeste Liu]

On 2025-10-27 19:36, Greg KH wrote:
> On Mon, Oct 20, 2025 at 08:25:30PM +0800, Celeste Liu wrote:
>> commit 2a27f6a8fb5722223d526843040f747e9b0e8060 upstream
>>
>> This issue was found by Runcheng Lu when develop HSCanT USB to CAN FD
>> converter[1]. The original developers may have only 3 interfaces
>> device to test so they write 3 here and wait for future change.
>>
>> During the HSCanT development, we actually used 4 interfaces, so the
>> limitation of 3 is not enough now. But just increase one is not
>> future-proofed. Since the channel index type in gs_host_frame is u8,
>> just make canch[] become a flexible array with a u8 index, so it
>> naturally constraint by U8_MAX and avoid statically allocate 256
>> pointer for every gs_usb device.
>>
>> [1]: https://github.com/cherry-embedded/HSCanT-hardware
>>
>> Fixes: d08e973a77d1 ("can: gs_usb: Added support for the GS_USB CAN devices")
>> Reported-by: Runcheng Lu <runcheng.lu@hpmicro.com>
>> Cc: stable@vger.kernel.org
>> Reviewed-by: Vincent Mailhol <mailhol@kernel.org>
>> Signed-off-by: Celeste Liu <uwu@coelacanthus.name>
>> Link: https://patch.msgid.link/20250930-gs-usb-max-if-v5-1-863330bf6666@coelacanthus.name
>> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
>> ---
>>  drivers/net/can/usb/gs_usb.c | 23 +++++++++++------------
>>  1 file changed, 11 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/net/can/usb/gs_usb.c b/drivers/net/can/usb/gs_usb.c
>> index 7dc4fb574e45..33800bb75064 100644
>> --- a/drivers/net/can/usb/gs_usb.c
>> +++ b/drivers/net/can/usb/gs_usb.c
>> @@ -157,10 +157,6 @@ struct gs_host_frame {
>>  #define GS_MAX_TX_URBS 10
>>  /* Only launch a max of GS_MAX_RX_URBS usb requests at a time. */
>>  #define GS_MAX_RX_URBS 30
>> -/* Maximum number of interfaces the driver supports per device.
>> - * Current hardware only supports 2 interfaces. The future may vary.
>> - */
>> -#define GS_MAX_INTF 2
>>  
>>  struct gs_tx_context {
>>  	struct gs_can *dev;
>> @@ -191,10 +187,11 @@ struct gs_can {
>>  
>>  /* usb interface struct */
>>  struct gs_usb {
>> -	struct gs_can *canch[GS_MAX_INTF];
>>  	struct usb_anchor rx_submitted;
>>  	struct usb_device *udev;
>>  	u8 active_channels;
>> +	u8 channel_cnt;
>> +	struct gs_can *canch[] __counted_by(channel_cnt);
>>  };
>>  
>>  /* 'allocate' a tx context.
>> @@ -322,7 +319,7 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
>>  	}
>>  
>>  	/* device reports out of range channel id */
>> -	if (hf->channel >= GS_MAX_INTF)
>> +	if (hf->channel >= usbcan->channel_cnt)
>>  		goto device_detach;
>>  
>>  	dev = usbcan->canch[hf->channel];
>> @@ -410,7 +407,7 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
>>  	/* USB failure take down all interfaces */
>>  	if (rc == -ENODEV) {
>>   device_detach:
>> -		for (rc = 0; rc < GS_MAX_INTF; rc++) {
>> +		for (rc = 0; rc < usbcan->channel_cnt; rc++) {
>>  			if (usbcan->canch[rc])
>>  				netif_device_detach(usbcan->canch[rc]->netdev);
>>  		}
>> @@ -993,20 +990,22 @@ static int gs_usb_probe(struct usb_interface *intf,
>>  	icount = dconf->icount + 1;
>>  	dev_info(&intf->dev, "Configuring for %d interfaces\n", icount);
>>  
>> -	if (icount > GS_MAX_INTF) {
>> +	if (icount > type_max(typeof(dev->channel_cnt))) {
>>  		dev_err(&intf->dev,
>> -			"Driver cannot handle more that %d CAN interfaces\n",
>> -			GS_MAX_INTF);
>> +			"Driver cannot handle more that %u CAN interfaces\n",
>> +			type_max(typeof(dev->channel_cnt)));
>>  		kfree(dconf);
>>  		return -EINVAL;
>>  	}
>>  
>> -	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
>> +	dev = kzalloc(struct_size(dev, canch, icount), GFP_KERNEL);
>>  	if (!dev) {
>>  		kfree(dconf);
>>  		return -ENOMEM;
>>  	}
>>  
>> +	dev->channel_cnt = icount;
>> +
>>  	init_usb_anchor(&dev->rx_submitted);
>>  
>>  	usb_set_intfdata(intf, dev);
>> @@ -1047,7 +1046,7 @@ static void gs_usb_disconnect(struct usb_interface *intf)
>>  		return;
>>  	}
>>  
>> -	for (i = 0; i < GS_MAX_INTF; i++)
>> +	for (i = 0; i < dev->channel_cnt; i++)
>>  		if (dev->canch[i])
>>  			gs_destroy_candev(dev->canch[i]);
>>  
>> -- 
>> 2.51.1.dirty
>>
>>
> 
> Breaks the build :(

Sorry, I have sent fixed version. And REALMODE_CFLAGS on x86 on linux-5.15.y
lacks -std flag, so it will build failed on GCC 15 because it use c23 by default
and the code try to typedef bool/true/false.

[PATCH 5.15.y] can: gs_usb: increase max interface to U8_MAX

[Celeste Liu]

commit 2a27f6a8fb5722223d526843040f747e9b0e8060 upstream

This issue was found by Runcheng Lu when develop HSCanT USB to CAN FD
converter[1]. The original developers may have only 3 interfaces
device to test so they write 3 here and wait for future change.

During the HSCanT development, we actually used 4 interfaces, so the
limitation of 3 is not enough now. But just increase one is not
future-proofed. Since the channel index type in gs_host_frame is u8,
just make canch[] become a flexible array with a u8 index, so it
naturally constraint by U8_MAX and avoid statically allocate 256
pointer for every gs_usb device.

[1]: https://github.com/cherry-embedded/HSCanT-hardware

Fixes: d08e973a77d1 ("can: gs_usb: Added support for the GS_USB CAN devices")
Reported-by: Runcheng Lu <runcheng.lu@hpmicro.com>
Cc: stable@vger.kernel.org
Reviewed-by: Vincent Mailhol <mailhol@kernel.org>
Signed-off-by: Celeste Liu <uwu@coelacanthus.name>
Link: https://patch.msgid.link/20250930-gs-usb-max-if-v5-1-863330bf6666@coelacanthus.name
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/usb/gs_usb.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/drivers/net/can/usb/gs_usb.c b/drivers/net/can/usb/gs_usb.c
index 7dc4fb574e45..ffa2a4d92d01 100644
--- a/drivers/net/can/usb/gs_usb.c
+++ b/drivers/net/can/usb/gs_usb.c
@@ -157,10 +157,6 @@ struct gs_host_frame {
 #define GS_MAX_TX_URBS 10
 /* Only launch a max of GS_MAX_RX_URBS usb requests at a time. */
 #define GS_MAX_RX_URBS 30
-/* Maximum number of interfaces the driver supports per device.
- * Current hardware only supports 2 interfaces. The future may vary.
- */
-#define GS_MAX_INTF 2
 
 struct gs_tx_context {
 	struct gs_can *dev;
@@ -191,10 +187,11 @@ struct gs_can {
 
 /* usb interface struct */
 struct gs_usb {
-	struct gs_can *canch[GS_MAX_INTF];
 	struct usb_anchor rx_submitted;
 	struct usb_device *udev;
 	u8 active_channels;
+	u8 channel_cnt;
+	struct gs_can *canch[];
 };
 
 /* 'allocate' a tx context.
@@ -322,7 +319,7 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
 	}
 
 	/* device reports out of range channel id */
-	if (hf->channel >= GS_MAX_INTF)
+	if (hf->channel >= usbcan->channel_cnt)
 		goto device_detach;
 
 	dev = usbcan->canch[hf->channel];
@@ -410,7 +407,7 @@ static void gs_usb_receive_bulk_callback(struct urb *urb)
 	/* USB failure take down all interfaces */
 	if (rc == -ENODEV) {
  device_detach:
-		for (rc = 0; rc < GS_MAX_INTF; rc++) {
+		for (rc = 0; rc < usbcan->channel_cnt; rc++) {
 			if (usbcan->canch[rc])
 				netif_device_detach(usbcan->canch[rc]->netdev);
 		}
@@ -993,20 +990,22 @@ static int gs_usb_probe(struct usb_interface *intf,
 	icount = dconf->icount + 1;
 	dev_info(&intf->dev, "Configuring for %d interfaces\n", icount);
 
-	if (icount > GS_MAX_INTF) {
+	if (icount > type_max(typeof(dev->channel_cnt))) {
 		dev_err(&intf->dev,
-			"Driver cannot handle more that %d CAN interfaces\n",
-			GS_MAX_INTF);
+			"Driver cannot handle more that %u CAN interfaces\n",
+			type_max(typeof(dev->channel_cnt)));
 		kfree(dconf);
 		return -EINVAL;
 	}
 
-	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	dev = kzalloc(struct_size(dev, canch, icount), GFP_KERNEL);
 	if (!dev) {
 		kfree(dconf);
 		return -ENOMEM;
 	}
 
+	dev->channel_cnt = icount;
+
 	init_usb_anchor(&dev->rx_submitted);
 
 	usb_set_intfdata(intf, dev);
@@ -1047,7 +1046,7 @@ static void gs_usb_disconnect(struct usb_interface *intf)
 		return;
 	}
 
-	for (i = 0; i < GS_MAX_INTF; i++)
+	for (i = 0; i < dev->channel_cnt; i++)
 		if (dev->canch[i])
 			gs_destroy_candev(dev->canch[i]);
 
-- 
2.51.1