Subject: Re: [PATCH net-next v6 1/3] ieee802154: cc2520: adds driver for TI CC2520 radio

From: Varka Bhadram <[email-masked]>
Date: Fri, 20 Jun 2014 15:58:00 +0530

Hi Alex,

On 06/20/2014 02:02 PM, Alexander Aring wrote:
> Hi Varka,
>
> sorry for my careful reviewing...,, but I had also some patch series
> which was at v8 or something like that. :-)

mhhh.. More careful review produces the best code ...

> On Fri, Jun 20, 2014 at 11:18:12AM +0530, Varka Bhadram wrote:
>> This patch adds the driver support for the cc2520 radio.
>>
>> Driver support:
>>          - Tx and Rx of IEEE-802.15.4 packets.
>>          - Energy Detection on channel.
>>          - Setting the Channel for the radio. [b/w 11 - 26 channels]
>>          - Start and Stop the radio
>>          - h/w address filtering.
>>
>> Signed-off-by: Varka Bhadram <[email-masked]>
>> ---
>>   drivers/net/ieee802154/cc2520.c | 1045 +++++++++++++++++++++++++++++++++++++++
>>   include/linux/spi/cc2520.h      |   26 +
>>   2 files changed, 1071 insertions(+)
>>   create mode 100644 drivers/net/ieee802154/cc2520.c
>>   create mode 100644 include/linux/spi/cc2520.h
>>
>> diff --git a/drivers/net/ieee802154/cc2520.c b/drivers/net/ieee802154/cc2520.c
>> new file mode 100644
>> index 0000000..fff7fd2
>> --- /dev/null
>> +++ b/drivers/net/ieee802154/cc2520.c
>> @@ -0,0 +1,1045 @@
>> +/* Driver for TI CC2520 802.15.4 Wireless-PAN Networking controller
>> + *
>> + * Copyright (C) 2014 Varka Bhadram <[email-masked]>
>> + *		      Md.Jamal Mohiuddin <[email-masked]>
>> + *		      P Sowjanya <[email-masked]>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License as published by
>> + * the Free Software Foundation; either version 2 of the License, or
>> + * (at your option) any later version.
>> + *
>> + */
>> +
> ...
>
>> +
>> +/* Driver private information */
>> +struct cc2520_private {
>> +	struct spi_device *spi;		/* spi device structure */
>> +	struct ieee802154_dev *dev;	/* Ieee802.15.4 device */
> why lowercase IEEE in the comment? :-)

Ok.

>> +	u8 *buf;			/* SPI TX/Rx data buffer */
>> +	struct mutex buffer_mutex;	/* SPI buffer mutex */
>> +	unsigned is_tx:1;		/* Flag for sync b/w Tx and Rx */
> bool/int?

I think there is no difference b/w 'unsigned' and 'unsigned int'. But it will be clear if we use 'unsigned int'

>> +	int fifo_pin;			/* FIFO GPIO pin number */
>> +	struct work_struct fifop_irqwork;/* Workqueue for FIFOP */
>> +	spinlock_t lock;		/* Spin lock */
> Everyone knows that this is a spinlock and I know checkpatch print some
> warning if there is a lock without comment. But they mean more "spinlock
> for what" in your case is_tx.

Ok.

> ...
>
>> +
>> +static int cc2520_rx(struct cc2520_private *priv)
>> +{
>> +	u8 len = 0, lqi = 0, bytes = 1;
>> +	struct sk_buff *skb;
>> +
>> +	cc2520_read_rxfifo(priv, &len, bytes, &lqi);
>> +
>> +	if (len < 2 || len > IEEE802154_MTU)
>> +		return -EINVAL;
>> +
>> +	skb = alloc_skb(len, GFP_KERNEL);
>> +	if (!skb)
>> +		return -ENOMEM;
>> +
>> +	if (cc2520_read_rxfifo(priv, skb_put(skb, len), len, &lqi)) {
>> +		pr_debug("frame reception failed\n");
> why pr_debug here? Use dev_dbg like the others, then we know which
> device this message prints.

Ok.

>> +		kfree_skb(skb);
>> +		return -EINVAL;
>> +	}
>> +
>> +	skb_trim(skb, skb->len - 2);
>> +
>> +	ieee802154_rx_irqsafe(priv->dev, skb, lqi);
>> +
>> +	dev_vdbg(&priv->spi->dev, "RXFIFO: %x %x\n", len, lqi);
>> +
>> +	return 0;
>> +}
>> +
> ...
>> +
>> +	ret = cc2520_register(priv);
>> +	if (ret)
>> +		goto err_hw_init;
>> +
>> +	return 0;
>> +
>> +err_hw_init:
>> +	mutex_destroy(&priv->buffer_mutex);
>> +	flush_work(&priv->fifop_irqwork);
>> +
>> +err_ret:
>> +	return ret;
>> +}
>> +
>> +static int cc2520_remove(struct spi_device *spi)
>> +{
>> +	struct cc2520_private *priv = spi_get_drvdata(spi);
>> +
>> +	ieee802154_unregister_device(priv->dev);
>> +	ieee802154_free_device(priv->dev);
>> +
>> +	mutex_destroy(&priv->buffer_mutex);
>> +	flush_work(&priv->fifop_irqwork);
> You need to call ieee802154_free_device at this point. The reason is
> that ieee802154_free_device free's your priv allocated data drom
> ieee802154_alloc_device. Did you test a "rmmod cc2520" with cc2520 as
> module support?

'rmmod cc2520' working fine for me. But we have to release the resources
in an opposite way that we requested them. Thanks, i will address this issue.

> Please do that and also verify that you need not to mask all interrupts
> before unloading (I had some experience with the at86rf230 chip). Means
> test "rmmod cc2520" while transmit some packages.
>
For this chip there are two GPIO's [FIFOP and SFD] serves our purpose of in Interrupt management.
I requested the IRQ channels on those GPIO (ofcourse i used gpio_to_irq()) pins.
Those will be freed (used devm_*) automatically.

In case of AT86rf230, there is IRQ_MASK register is used to enable (set register bit to 1)
or disable (set register bit to 0) interrupt events. That configuration is not available for CC2520.

Thanks for the comments. I will address these issues in v7.

-Varka Bhadram

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