linux-kernel - Re: [PATCH v1] misc: fastrpc: Add support for multiple PD from one process

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Message-ID: <c4a184cb-46d5-49cc-ad42-3d5d7828f06b@quicinc.com>
Date: Thu, 4 Jul 2024 11:47:22 +0530
From: Ekansh Gupta <quic_ekangupt@...cinc.com>
To: Greg KH <gregkh@...uxfoundation.org>
CC: <srinivas.kandagatla@...aro.org>, <linux-arm-msm@...r.kernel.org>,
        <quic_bkumar@...cinc.com>, <linux-kernel@...r.kernel.org>,
        <quic_chennak@...cinc.com>, <dri-devel@...ts.freedesktop.org>,
        <arnd@...db.de>
Subject: Re: [PATCH v1] misc: fastrpc: Add support for multiple PD from one
 process



On 7/3/2024 4:09 PM, Greg KH wrote:
> On Wed, Jul 03, 2024 at 12:22:00PM +0530, Ekansh Gupta wrote:
>> @@ -268,6 +272,7 @@ struct fastrpc_channel_ctx {
>>  	struct fastrpc_session_ctx session[FASTRPC_MAX_SESSIONS];
>>  	spinlock_t lock;
>>  	struct idr ctx_idr;
>> +	struct ida dsp_pgid_ida;
> You have an idr and an ida?  Why two different types for the same
> driver?
Using ida for this because for this I just need to allocate and manage unique IDs
without any associated data. So this looks more space efficient that idr.
Should I keep it uniform for a driver?
>
>>  	struct list_head users;
>>  	struct kref refcount;
>>  	/* Flag if dsp attributes are cached */
>> @@ -299,6 +304,7 @@ struct fastrpc_user {
>>  	struct fastrpc_buf *init_mem;
>>  
>>  	int tgid;
>> +	int dsp_pgid;
> Are you sure this fits in an int?
I think this should be fine for IDs in rage of 1000-1064.
>
>> +static int fastrpc_pgid_alloc(struct fastrpc_channel_ctx *cctx)
>> +{
>> +	int ret = -1;
> No need to initialize this.
I'll update this.
>
>> +
>> +	/* allocate unique id between MIN_FRPC_PGID and MAX_FRPC_PGID */
>> +	ret = ida_alloc_range(&cctx->dsp_pgid_ida, MIN_FRPC_PGID,
>> +					MAX_FRPC_PGID, GFP_ATOMIC);
>> +	if (ret < 0)
>> +		return -1;
> Why is -1 a specific value here?  Return a real error please.
> Or return 0 if that's not allowed.
Sure, will fix this in next spin.
>
> v
>> +
>> +	return ret;
>> +}
>> +
>>  static int fastrpc_device_open(struct inode *inode, struct file *filp)
>>  {
>>  	struct fastrpc_channel_ctx *cctx;
>> @@ -1582,6 +1605,12 @@ static int fastrpc_device_open(struct inode *inode, struct file *filp)
>>  	fl->cctx = cctx;
>>  	fl->is_secure_dev = fdevice->secure;
>>  
>> +	fl->dsp_pgid = fastrpc_pgid_alloc(cctx);
>> +	if (fl->dsp_pgid == -1) {
>> +		dev_dbg(&cctx->rpdev->dev, "too many fastrpc clients, max %u allowed\n", MAX_DSP_PD);
>> +		return -EUSERS;
> Why -EUSERS?
This should be -EBUSY, I'll correct this.
>
> And you obviously did not test this as you just leaked memory :(
My bad, I ran basic fastrpc tests and the working of this use case. Sorry for the miss.

--Ekansh
>
> thanks,
>
> greg k-h