Re: [PATCH v2 2/2] USB: storage: ums-realtek: Make auto-delink support optionally

From: Kai-Heng Feng
Date: Tue Aug 27 2019 - 12:47:18 EST


at 23:55, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:

On Mon, 26 Aug 2019, Kai-Heng Feng wrote:

Auto-delink requires writing special registers to ums-realtek device.
Unconditionally enable auto-delink may break newer devices.

So only enable auto-delink by default for the original three IDs,
0x0138, 0x0158 and 0x0159.

Realtek is working on a patch to properly support auto-delink for other
IDs.

BugLink: https://bugs.launchpad.net/bugs/1838886
Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
---
v2:
- Use auto_delink_support instead of auto_delink_enable.

drivers/usb/storage/realtek_cr.c | 24 +++++++++++++++++++-----
1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/storage/realtek_cr.c b/drivers/usb/storage/realtek_cr.c
index beaffac805af..b304cca7c4fa 100644
--- a/drivers/usb/storage/realtek_cr.c
+++ b/drivers/usb/storage/realtek_cr.c
@@ -40,6 +40,10 @@ static int auto_delink_en = 1;
module_param(auto_delink_en, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(auto_delink_en, "auto delink mode (0=firmware, 1=software [default])");

+static int auto_delink_support = -1;
+module_param(auto_delink_support, int, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(auto_delink_support, "enable auto delink (-1=auto [default], 0=disable, 1=enable)");
+
#ifdef CONFIG_REALTEK_AUTOPM
static int ss_en = 1;
module_param(ss_en, int, S_IRUGO | S_IWUSR);
@@ -996,12 +1000,22 @@ static int init_realtek_cr(struct us_data *us)
goto INIT_FAIL;
}

- if (CHECK_FW_VER(chip, 0x5888) || CHECK_FW_VER(chip, 0x5889) ||
- CHECK_FW_VER(chip, 0x5901))
- SET_AUTO_DELINK(chip);
- if (STATUS_LEN(chip) == 16) {
- if (SUPPORT_AUTO_DELINK(chip))
+ if (auto_delink_support == -1) {
+ if (CHECK_PID(chip, 0x0138) || CHECK_PID(chip, 0x0158) ||
+ CHECK_PID(chip, 0x0159))
+ auto_delink_support = 1;
+ else
+ auto_delink_support = 0;
+ }

What will happen if somebody has two Realtek devices plugged in, where
one of them has an old product ID and the other has a new one? You
shouldn't change the value of the module parameter like this.

You are right, I didnât think of that.


+
+ if (auto_delink_support) {
+ if (CHECK_FW_VER(chip, 0x5888) || CHECK_FW_VER(chip, 0x5889) ||
+ CHECK_FW_VER(chip, 0x5901))
SET_AUTO_DELINK(chip);
+ if (STATUS_LEN(chip) == 16) {
+ if (SUPPORT_AUTO_DELINK(chip))
+ SET_AUTO_DELINK(chip);
+ }
}
#ifdef CONFIG_REALTEK_AUTOPM
if (ss_en)

Instead of adding a new module parameter, how about just changing the
driver's behavior? If a chip doesn't have the right product ID, don't
enable auto_delink regardless of what the module parameter is set to.

Ok, I think whitelist is a better approach until Realtek comes up with a long term solution.

Kai-Heng


Alan Stern