linux-kernel - RE: RE: [PATCH v2 2/4] extcon: Added extcon_alloc_cables to simplify extcon register function

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Date:   Thu, 2 Mar 2023 16:12:06 +0900
From:   "Bumwoo Lee" <bw365.lee@...sung.com>
To:     <myungjoo.ham@...sung.com>,
        "'Chanwoo Choi'" <cw00.choi@...sung.com>,
        <linux-kernel@...r.kernel.org>
Subject: RE: RE: [PATCH v2 2/4] extcon: Added extcon_alloc_cables to
 simplify extcon register function


> -----Original Message-----
> From: MyungJoo Ham <myungjoo.ham@...sung.com>
> Sent: Thursday, March 2, 2023 3:33 PM
> To: Bumwoo Lee <bw365.lee@...sung.com>; Chanwoo Choi
> <cw00.choi@...sung.com>; linux-kernel@...r.kernel.org
> Subject: RE: RE: [PATCH v2 2/4] extcon: Added extcon_alloc_cables to
> simplify extcon register function
> 
> >
> >
> >--------- Original Message ---------
> >Sender : 이범우 <bw365.lee@...sung.com>Product S/W Lab(VD)/삼성전자 Date :
> >2023-03-02 10:38 (GMT+9) Title : RE: [PATCH v2 2/4] extcon: Added
> >extcon_alloc_cables to simplify extcon register function
> >
> >Hello.
> >
> >As you can see, edev->cables are freed if extcon_alloc_cables()
> >function return error handling in extcon_dev_register() Other added
> functions are also same.
> >
> >Because it's functionalized, apart from this, do you want to mention that
> it should be freed within the function?
> >Please let me know your opinion.
> >
> >extcon_dev_register(struct extcon_dev *edev){ ...
> >
> >        ret = extcon_alloc_cables(edev);
> >        if (ret)
> >                goto err_alloc_cables;
> >
> >...
> >
> >err_alloc_cables:
> >         if (edev->max_supported)
> >                 kfree(edev->cables);
> >
> >
> >Regards,
> >Bumwoo
> 
> In such a case, you are doing kfree(NULL); with the following:

Yes, you are right.
But Kfree() is checking NULL internally. So it does not a problem I think.
Anyway I added kfree(edev->cables) before exit extcon_alloc_cables() like below on v3 patches.

static int extcon_alloc_cables(struct extcon_dev *edev) {
...
                         for (index--; index >= 0; index--) {
                                 cable = &edev->cables[index];
                                 kfree(cable->attr_g.name);
                         }
 
+                        kfree(edev->cables);
                         return -ENOMEM;
                 }



> >+static int extcon_alloc_cables(struct extcon_dev *edev) {
> ...
> >+        if (!edev->max_supported)
> >+                return 0;
> >+
> >+        edev->cables = kcalloc(edev->max_supported,
> >+                               sizeof(struct extcon_cable),
> >+                               GFP_KERNEL);
> >+        if (!edev->cables)
> >+                return -ENOMEM;
> 
> 
> 
> 
> Cheers,
> MyungJoo
> 

Regards,
Bumwoo