On 25.05.2021 14:12, Jean Delvare wrote:
> Hi Heiner,
>
> Adding Daniel Kurtz, who wrote the original wait queue-based code, to
> Cc. I'm not sure if Daniel is still into kernel code though.
>
> On Sat, 22 May 2021 00:02:43 +0200, Heiner Kallweit wrote:
>> Using the completion API is more intuitive and it allows to simplify
>> the code. Note that we don't have to set priv->status = 0 any longer
>> with the completion API.
>
> OK, but you need to call reinit_completion() instead, which has the
> same cost. So that's not a good argument ;-)
>
Maybe my comment wasn't clear enough. I didn't want to say that we
save something but that it's safe from a functional point of view
to remove clearing priv->status.
>> Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
>> ---
>> drivers/i2c/busses/i2c-i801.c | 48 ++++++++++++++---------------------
>> 1 file changed, 19 insertions(+), 29 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
>> index bfea94d02..738204d77 100644
>> --- a/drivers/i2c/busses/i2c-i801.c
>> +++ b/drivers/i2c/busses/i2c-i801.c
>> @@ -103,7 +103,7 @@
>> #include <linux/dmi.h>
>> #include <linux/slab.h>
>> #include <linux/string.h>
>> -#include <linux/wait.h>
>> +#include <linux/completion.h>
>> #include <linux/err.h>
>> #include <linux/platform_device.h>
>> #include <linux/platform_data/itco_wdt.h>
>> @@ -270,7 +270,7 @@ struct i801_priv {
>> unsigned int features;
>>
>> /* isr processing */
>> - wait_queue_head_t waitq;
>> + struct completion done;
>> u8 status;
>>
>> /* Command state used by isr for byte-by-byte block transactions */
>> @@ -496,24 +496,19 @@ static int i801_wait_byte_done(struct i801_priv *priv)
>> static int i801_transaction(struct i801_priv *priv, int xact)
>> {
>> int status;
>> - int result;
>> + unsigned long result;
>> const struct i2c_adapter *adap = &priv->adapter;
>>
>> - result = i801_check_pre(priv);
>> - if (result < 0)
>> - return result;
>> + status = i801_check_pre(priv);
>> + if (status < 0)
>> + return status;
>>
>> if (priv->features & FEATURE_IRQ) {
>> + reinit_completion(&priv->done);
>> outb_p(xact | SMBHSTCNT_INTREN | SMBHSTCNT_START,
>> SMBHSTCNT(priv));
>> - result = wait_event_timeout(priv->waitq,
>> - (status = priv->status),
>> - adap->timeout);
>> - if (!result)
>> - status = -ETIMEDOUT;
>> -
>> - priv->status = 0;
>> - return i801_check_post(priv, status);
>> + result = wait_for_completion_timeout(&priv->done, adap->timeout);
>> + return i801_check_post(priv, result ? priv->status : -ETIMEDOUT);
>> }
>>
>> /* the current contents of SMBHSTCNT can be overwritten, since PEC,
>> @@ -638,7 +633,7 @@ static irqreturn_t i801_host_notify_isr(struct i801_priv *priv)
>> * DEV_ERR - Invalid command, NAK or communication timeout
>> * BUS_ERR - SMI# transaction collision
>> * FAILED - transaction was canceled due to a KILL request
>> - * When any of these occur, update ->status and wake up the waitq.
>> + * When any of these occur, update ->status and signal completion.
>> * ->status must be cleared before kicking off the next transaction.
>> *
>> * 2) For byte-by-byte (I2C read/write) transactions, one BYTE_DONE interrupt
>> @@ -675,7 +670,7 @@ static irqreturn_t i801_isr(int irq, void *dev_id)
>> if (status) {
>> outb_p(status, SMBHSTSTS(priv));
>> priv->status = status;
>> - wake_up(&priv->waitq);
>> + complete(&priv->done);
>> }
>>
>> return IRQ_HANDLED;
>> @@ -694,15 +689,15 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
>> int i, len;
>> int smbcmd;
>> int status;
>> - int result;
>> + unsigned long result;
>> const struct i2c_adapter *adap = &priv->adapter;
>>
>> if (command == I2C_SMBUS_BLOCK_PROC_CALL)
>> return -EOPNOTSUPP;
>>
>> - result = i801_check_pre(priv);
>> - if (result < 0)
>> - return result;
>> + status = i801_check_pre(priv);
>> + if (status < 0)
>> + return status;
>>
>> len = data->block[0];
>>
>> @@ -726,15 +721,10 @@ static int i801_block_transaction_byte_by_byte(struct i801_priv *priv,
>> priv->count = 0;
>> priv->data = &data->block[1];
>>
>> + reinit_completion(&priv->done);
>> outb_p(priv->cmd | SMBHSTCNT_START, SMBHSTCNT(priv));
>> - result = wait_event_timeout(priv->waitq,
>> - (status = priv->status),
>> - adap->timeout);
>> - if (!result)
>> - status = -ETIMEDOUT;
>> -
>> - priv->status = 0;
>> - return i801_check_post(priv, status);
>> + result = wait_for_completion_timeout(&priv->done, adap->timeout);
>> + return i801_check_post(priv, result ? priv->status : -ETIMEDOUT);
>> }
>>
>> for (i = 1; i <= len; i++) {
>> @@ -1889,7 +1879,7 @@ static int i801_probe(struct pci_dev *dev, const struct pci_device_id *id)
>> }
>>
>> if (priv->features & FEATURE_IRQ) {
>> - init_waitqueue_head(&priv->waitq);
>> + init_completion(&priv->done);
>>
>> err = devm_request_irq(&dev->dev, dev->irq, i801_isr,
>> IRQF_SHARED,
>
> The clean-up isn't massive but I agree the code is a bit more pleasant
> to read after the change, and I also see the binary size shrink a bit,
> so I vote for it.
>
> Reviewed-by: Jean Delvare <jdelvare@xxxxxxx>
> Tested-by: Jean Delvare <jdelvare@xxxxxxx>
>
