Re: [PATCH v8 03/22] counter: 104-quad-8: Return error when invalid mode during ceiling_write

From: David Lechner
Date: Sat Feb 20 2021 - 11:31:12 EST


On 2/12/21 6:13 AM, William Breathitt Gray wrote:
The 104-QUAD-8 only has two count modes where a ceiling value makes
sense: Range Limit and Modulo-N. Outside of these two modes, setting a
ceiling value is an invalid operation -- so let's report it as such by
returning -EINVAL.

Fixes: fc069262261c ("counter: 104-quad-8: Add lock guards - generic interface")
Cc: Syed Nayyar Waris <syednwaris@xxxxxxxxx>
Signed-off-by: William Breathitt Gray <vilhelm.gray@xxxxxxxxx>
---
drivers/counter/104-quad-8.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/counter/104-quad-8.c b/drivers/counter/104-quad-8.c
index 9691f8612be8..f0608b21196a 100644
--- a/drivers/counter/104-quad-8.c
+++ b/drivers/counter/104-quad-8.c
@@ -714,13 +714,14 @@ static ssize_t quad8_count_ceiling_write(struct counter_device *counter,
switch (priv->count_mode[count->id]) {
case 1:
case 3:
+ mutex_unlock(&priv->lock);
quad8_preset_register_set(priv, count->id, ceiling);
- break;
+ return len;
}
mutex_unlock(&priv->lock);
- return len;
+ return -EINVAL;
}
static ssize_t quad8_count_preset_enable_read(struct counter_device *counter,


What happens if the register is written to when in the wrong mode?

If it doesn't hurt anything, I would suggest always writing the register
instead so that users don't have to know worry about the fact that the mode
has to be set first.