[PATCH 1/2] thunderbolt: allow vendor ID override for NVM programming

["Francisco Blas Izquierdo Riera (klondike)" <klondike@klondike.es>]

Currently, the vendor ID reported by the chipset is checked before to
avoid accidentally programming devices from unsupported vendors with
a different NVM structure.

Certain Thunderbolt devices store the vendor ID in the NVM, therefore
if the NVM has become corrrupted the device will report an invalid
vendor ID and reflashing will be impossible on GNU/Linux even if the
device can boot in safe mode.

This patch adds a new parameter ``switch_nvm_vendor_override`` which
can be used to override the vendor ID used for detecting the NVM
structure allowing to reflash (and authenticate) a new, valid
image on the device.

Signed-off-by: Francisco Blas Izquierdo Riera (klondike) <klondike@klondike.es>
---
drivers/thunderbolt/switch.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index 3014146081..a7959c3f3f 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -13,6 +13,7 @@
#include <linux/sched/signal.h>
#include <linux/sizes.h>
#include <linux/slab.h>
+#include <linux/moduleparam.h>
#include "tb.h"
@@ -34,6 +35,10 @@ struct nvm_auth_status {
static LIST_HEAD(nvm_auth_status_cache);
static DEFINE_MUTEX(nvm_auth_status_lock);
+static short switch_nvm_vendor_override = -1;
+module_param(switch_nvm_vendor_override, short, 0440);
+MODULE_PARM_DESC(switch_nvm_vendor_override, "Override the switch vendor id on the nvm access routines");
+
static struct nvm_auth_status *__nvm_get_auth_status(const struct tb_switch *sw)
{
struct nvm_auth_status *st;
@@ -391,7 +396,9 @@ static int tb_switch_nvm_add(struct tb_switch *sw)
* relax this in the future when we learn other NVM formats.
*/
if (sw->config.vendor_id != PCI_VENDOR_ID_INTEL &&
- sw->config.vendor_id != 0x8087) {
+ sw->config.vendor_id != 0x8087 &&
+ switch_nvm_vendor_override != PCI_VENDOR_ID_INTEL &&
+ switch_nvm_vendor_override != 0x8087) {
dev_info(&sw->dev,
"NVM format of vendor %#x is not known, disabling NVM upgrade\n",
sw->config.vendor_id);